Personality, psychosocial risks at work, and health
Transcription
Personality, psychosocial risks at work, and health
Personality, psychosocial risks at work, and health Katharine Parkes, PhD Department of Experimental Psychology, University of Oxford, UK A report prepared for the “Collège d’expertise sur le suivi statistique des risques psychosociaux au travail” and commissioned by the DREES March 2010 Summary This report responds to questions formulated by the Expert Committee about the role of personality in the process whereby work-related psychosocial risk factors are implicated in mental and physical health impairment. There are four main parts to the report. In Section 1, as a background to the specific questions raised, models of work stress are described, and the various pathways by which personality and work-related psychosocial factors jointly impact on health, are examined with reference to empirical findings. Section 2 documents a systematic review of journal articles (published 20002009) describing prospective studies that evaluate work-related psychosocial risks and one or more personality measures as predictors of mental and physical health outcomes. A total of 33 studies which met these and other pre-determined criteria were identified. Findings from the studies are summarised and discussed, with particular reference to evidence of the additive, interactive, and mediator roles of personality in relations between psychosocial risk factors and health outcomes. Section 3 responds to a further question concerned with changes in personality across the life course. Normative age-related changes in mean levels of personality variables are described, and work-related factors associated with individual change are considered, noting evidence of reciprocal influence between work experiences and personality change. Psychometric issues relevant to the development and validation of personality measures are outlined in Section 4, and the psychometric properties of several widely-used measures are described in Section 5. Particular attention is given to evidence of the reliability and validity of the personality measures identified in Section 2 as significant predictors of health outcomes in the prospective studies reviewed. Examples of personality measures available in the published literature, and the scoring methods used, are shown in the Appendix. Index 1. Introduction 1.1 Demand-control-support model 1.2 Effort-reward imbalance model 1.3 Organizational justice model 1.4 The role of personality in work stress 1 1 2 2 2. Psychosocial risks, personality and health: A systematic review 2.1 Background 2.2 Literature search 2.3 Results 2.4 Findings for individual personality characteristics 2.5 Conclusions 8 10 12 14 20 3. Personality change over the life course 3.1 Mean-level changes in personality across the life course 3.2 Individual differences in patterns of personality change 3.3 Implications 41 44 46 4. Psychometric issues: Reliability and validity of personality tests 4.1 Scale development 4.2 Reliability and validity 4.3 Fairness in psychometric testing 48 48 49 5. Psychometric properties of specific personality measures 5.1 The NEO Five-Factor personality measures 5.2 Over-commitment 5.3 Negative affectivity 5.4 Hostility 5.5 Sense of coherence 5.6 Locus of control 5.7 Core self evaluations 5.8 General issues 50 52 54 56 58 60 61 62 6. References 64 Appendix: Examples of selected tests 80 1 1. Introduction Evidence from prospective studies shows that exposure to work-related psychosocial risks has an adverse impact on long-term health. Much of this evidence comes from research based on two current models of work stress, the job demand-control-support model (DCS)1 and the Effort-Reward model (ERI)2. These main features of these models, together with a more recent model, the Organizational Justice model3, are outlined below. 1.1 Demand-control-support model In the DCS model, high demands (e.g. time pressures, work overload), low control (few opportunities to make decisions at work, limited skill utilization), and low social support are predicted to lead to high psycho-physiological strain and, over time, to adverse health outcomes. The significance of the DCS dimensions for health outcomes, particularly cardiovascular disease4-6 and affective well-being7-9 has been widely demonstrated. Significant findings have also been reported for other outcome measures, including minor health complaints10, workability11, absenteeism12, and suicide/attempted suicide13,14. However, the relative importance of the three DCS dimensions in predicting health outcomes varies across studies. Moreover, concerns have been raised about methodological limitations, particularly in relation to cross-sectional survey studies 7,15. Relatively little evidence supports the demand x control interaction originally predicted by the job strain model16; a review of ‘high quality’ longitudinal studies concluded that there was only modest support for the interactive hypothesis7. More usually, additive effects are reported17,18. 1.2 Effort-reward imbalance model The ERI model proposes that an imbalance between effort (e.g. extrinsic job demands, responsibilities, and obligations) and rewards (money, promotion prospects, job security) is a risk factor for poor health2. Unlike the DCS model, recent versions of the ERI model include an intrinsic personality component, designated ‘over-commitment’ (OC). The nature and hypothesised role of OC has evolved in the development of the ERI model; it now refers to a personality trait combining excessive striving with needs for approval and esteem, and is regarded as a potential moderator variable19. Findings from prospective studies support the ERI model in that high effort coupled with low reward is associated with poor mental and physical (particularly cardiovascular) health 20,21. Job insecurity has been found to add to the adverse effects of ERI22. However, a recent study questions the value of combining effort and reward into a single measure23, and other evidence suggests that causal relations between ERI and health may be reciprocal rather than unidirectional24. The role of over-commitment has been less widely examined, but it was found to be significant as an additive risk factor, over and above ERI measures, in four out of five studies of CVD incidence, and in five out of eleven studies of CVD symptoms in a review 2 of ERI research19. However, the review provided little support for the interactive model although a more recent survey, using measures from both the ERI and the DCS models, reported that low control (DCS model) and high OC (ERI model) combined synergistically to give rise to a high levels of depressive symptoms25. 1.3 Organizational justice model Lack of organizational justice in the workplace has been recognised as a psychosocial risk factor that can lead to adverse mental and physical health outcomes3. The ‘Organizational Justice’ model has two components, procedural injustice (decisions at work lack consistency, openness and input from all affected parties) and relational injustice (lack of considerate and fair treatment of employees by supervisors); these components have been found to predict sleeping problems26, poor mental health27 and cardiovascular mortality28 in prospective studies and to explain variance in health outcomes over and above that accounted for by ERI measures27. 1.4 The role of personality in work stress The models outlined above do not incorporate individual personality characteristics as predictors of mental and physical health outcomes (with the exception of the OC measure in the ERI model). However, personality is known to be significant in relation to longterm health29-31, and several work stress models include paths among personality traits, objective and perceived work stressors and health outcomes. One such model, the ‘Michigan’ model32,33 has been particularly influential in guiding research into the joint effects of personality variables and psychosocial work stressors, and is used as the basis for the present discussion. As represented in this model, shown in Figure 1.1, objective work characteristics influence subjective perceptions of work stress; these perceptions give rise to short-term affective, cognitive, behavioural and physiological responses which, with continued stressor exposure, lead to chronic long-term health impairment. However, the model also incorporates bi-directional pathways and feedback loops; for instance, long-term health impairment may lead individuals to perceive their work conditions less favourably, or to seek an objectively less demanding job. The influence of individual differences operates at several points in the stress process represented by the Michigan model. For instance, personality traits (and other individual characteristics) may act by influencing selection into different types of job and hence exposure to objective stressors40, or by influencing work perceptions34, or by directly influencing stress responses and health35,36. Moreover, the model includes not only direct effects of personality, but also mediating and moderating effects, and bi-directional paths. Personality variables, particularly negative affectivity, are potentially involved in each of these mechanisms37. MODERATOR VARIABLES: INDIVIDUAL AND SITUATIONAL CHARACTERISTICS Social support Management style Personality Coping resources Demographic e.g. age, gender, education Objective work stressors Work overload Long work hours Paced work, time pressures Lack of control over work tasks Shift work Organizational re-structuring, down-sizing, job insecurity Behavioural e.g. exercise diet Short-term responses Perceived work stressors Genetic e.g. family history of illness Long-term outcomes Affective Medical Cognitive Psychological Behavioural Physiological e.g. Cardiovascular disease e.g. Chronic depression Anxiety disorder Behavioural e.g. Alcoholism Figure 1.1 Conceptual model of the stress process Note: Solid lines represent direct effects among variables. Broken lines represent interaction effects. Adapted from Israel et al. (1996) 3 4 1.4.1 Personality and work stress: Mediating effects Mediation refers to an indirect process by which the effect of one variable on an outcome measure is transmitted through an intervening variable (see Baron and Cohen38 for statistical methods of testing mediation effects). Thus, personality may influence how individuals perceive the objective work demands to which they are exposed and these perceptions in turn may lead to short-term affective, physiological, and behavioural responses, and eventually to chronic health effects. In this presumed sequence, the effects of personality on long-term health are mediated through perceived work stressors and short-term stress responses. In a longitudinal study of mediation effects using a cross-lagged panel design, Schwarzer et al.39 examined the role of self-efficacy in the process by which work stress led to burnout in teachers. The results showed that self-efficacy was a protective factor; resourceful individuals high in self-efficacy experienced less job stress, which in turn reduced subsequent burnout. Moreover, over the one-year follow-up period, the path from earlier self-efficacy to later burnout was stronger than the (non-significant) reverse causal path. Similarly, a measure of personality resources assessed in childhood and early adulthood was found to predict job satisfaction in middle adulthood, and this relationship was partially mediated by job complexity40. A different form of mediation was reported by Kivimaki et al.41 from a 7 yr follow-up study of hostility and sickness absence in which the personality variable ‘Sense of Coherence’ (SOC)42 acted as mediator, reducing the association between individual hostility and subsequent sickness absence by 33-50% depending on the outcome measure. In a further study, Feldt et al.43 found that the longitudinal relationship between psychosocial stressors (including job insecurity) and psychosomatic/affective outcomes was mediated by SOC. These two studies suggest that change in SOC may result from exposure to individual and work-related psychosocial factors. 1.4.2 Personality and work stress: Confounding effects As used in work stress research, the term ‘confounding’ refers to the role of personality traits (or other factors such as demographic or socioeconomic variables) in creating an apparent link between measures of work-related psychosocial risks and health, which may be solely or partly due to a ‘third factor’ effect, the influence of the confounding variable(s) on both perceptions of job characteristics and health. In relation to personality, attention has been focused primarily on neuroticism/NA as a potential confounding factor, i.e. as a source of self-report bias that should be statistically controlled in studies that seek to link perceived job stressors and health outcomes44,45. Accordingly, self-report studies of psychosocial stressors and strain responses often include NA as a control variable46,47. If inclusion of NA in a multivariate analysis reduces the relationship between perceived stressors and outcome, then confounding is a possible explanation (although it should be noted that the statistical test for confounding is the same as that for mediation; interpretation depends on the nature of the variables concerned, and the underlying theoretical viewpoint). 5 The view that NA is simply a ‘nuisance’ variable and a potential source of bias has been disputed by other researchers, particularly Spector and his colleagues34,48, who argue that there is little evidence to support a general bias effect that cuts across all stressor and strain variables. They suggest that NA plays an important role in work stress processes which should be addressed rather than statistically controlled, and they describe a series of substantive mechanisms through which NA could affect job stressors and strains, each supported by research evidence34: • • • • • • Perception. This mechanism reflects the tendency of individuals high in NA to view the world in a negative light, but their negative self-reports of job stressors are seen as valid indicators of their actual perceptions and experiences. Hyper-responsivity. High NA individuals may respond to the same objective level of stressors more strongly than their low NA counterparts, in which case NA would act as a moderating variable in relations between job stressors and affective responses. Selection. High NA individuals may be in more stressful jobs than those low in NA, because they are recruited for less favourable jobs, or because of self-selection. Stressor creation. High NA individuals may, by their own behaviour, create job stressors for themselves, for example, by creating interpersonal conflicts at work, or by managing their workload less effectively than low NA individuals. Mood. Transitory mood may affect the assessment of NA. If so, and if mood is also affected by job conditions, then a correlation between NA and job stressors could reflect the indirect influence of job stressors on reports of NA, rather than the effects of NA on reports of job stressors. Causality. Exposure to high levels of job stressors may tend to make individuals higher in NA; thus, this mechanism proposes that job characteristics affect the trait level of NA, as assessed empirically. Whilst these possible mechanisms are discussed in relation to NA by Spector et al.34, they are not necessarily specific to NA; for example, Hoge et al.49 found that sense of coherence had not only direct effects on strain measures, but also showed significant perception, selection, and stressor-creation effects, although work stressors remained substantial predictors of strain. 1.4.3 Personality and work stress: Reciprocal effects and reverse causation Although theoretical models represent job stressors as having a causal effect on health outcomes, evidence of reciprocal and reverse causal relationships between work-related psychosocial risk factors and health outcomes is increasing. In some instances, also, personality variables are implicated in these reverse or reciprocal relationships. A review of longitudinal field studies of organizational stress, found that about half of the 43 studies evaluated reverse causation in stressor-strain relationships, and some evidence of reversed causal effects was found in about 33% of the studies concerned50. More recently, in an evaluation of the demand-control model, Dalgard et al.51 found evidence of reverse causation over an 11-yr follow-up period; in this case, it applied to job demands but not to job control. 6 Several studies have applied structural modelling to longitudinal panel data which allows evaluation not only of direct and reverse causation but also of reciprocal causal effects between exposures and health measures. Although at least one study using structural modelling has affirmed the theoretical causal ordering among DCS job characteristics and work-related psychological well-being52, reciprocal longitudinal findings have also been reported53. Similarly, in an evaluation of cross-lagged reciprocal relationships among job demands, work-home interference, and general health, a reciprocal model proved to be superior to both the direct causation and the reversed causation models54. Structural modelling has also been used to evaluate causal paths between ERI measures and health; using three waves of data collection, Shimazu et al.24 found cross-lagged and causally dominant effects of ERI on employee psychological and physical health, but also evidence of reciprocal effects. Similarly, Xanthopoulou et al.55 found that the best-fit model was one in which not only were personal resources (self-esteem, self-efficacy and optimism) and job resources (e.g. autonomy, support) reciprocally related to work engagement, but there was also a reciprocal relationship between job and personal resources. Taken together, these longitudinal studies do not provide strong support for uni-directional reverse causal paths from strains to stressors although, consistent with the ERI and DCS theoretical models, there is evidence of causal influences from psychosocial stressors to health-related outcomes. However, it is also clear that reciprocal paths play an important role in stressor-strain relationships; moreover, these reciprocal pathways may involve personality variables in addition to measures of psychosocial risk factors and health. Thus, even though personality characteristics are conceptualised to be stable over time, as empirically assessed, they appear to be subject to influence by work conditions over relatively short time periods. 1.4.4 Personality and work stress: Interactive effects Additive (or main) effects imply that two or more predictor variables contribute independently to explaining variance in an outcome measure; in contrast, interactive (or moderating) effects imply that the magnitude and direction of the effect of one predictor (for example, a psychosocial risk factor) on a outcome measure depends on the level of a second predictor (for example, a personality characteristic). Two forms of interaction can be identified, ‘vulnerability/resilience’ and ‘person-environment fit’. • Vulnerability implies that a high level of a maladaptive personality trait if combined with a high level of a psychosocial risk factor will result in a disproportionately adverse outcome relative to their additive effects. Thus, for instance, high NA individuals were found to show significantly greater reactivity to high job demands than low NA subjects56. Conversely, resilience or buffering implies that a high level of an adaptive personality resource protects individuals from adverse effects of exposure to psychosocial risk factors. 7 • Person-environment fit. In cross-over interactions, neither high nor low levels of a personality factor are necessarily maladaptive; rather, adverse outcomes arise from incongruence or ‘lack of fit’ between personality and the environment. For instance, perceived job control and an individual’s locus of control may be congruent or incongruent, and have favorable or unfavorable effects, respectively, on outcomes57. Although the DCS model does not include personality variables, evidence that personality characteristics may act as moderators of the effects of exposure to high strain (or high isostrain) conditions has been reported. For instance, a significant three-way interaction was found to predict affective well-being in cross-sectional and longitudinal data58; demand and control combined interactively for externals whereas additive effects were found for internals. Other researchers have also found that personality characteristics moderate the effects of DCS dimensions on health outcomes57,59, and have advocated further research to extend the demand/control model with personal characteristics59. The points in the causal process at which personality may moderate work stress effects are not yet clearly established. In particular, moderating variables may influence either or both links in the paths by which objective stressors influence perceptions of work stress, and perceptions of work stress are related to psychological and physiological responses. In particular, little is known about how personality variables may moderate relations between objective and perceived work stressors, although significant dispositional moderators of relations between objective and perceived characteristics of laboratory tasks have been identified60. 8 2. 2.1 Psychosocial risks, personality and health: A systematic review Background Over the past five years, prospective research into psychosocial risk factors in relation to physical and mental health outcomes has been the subject of several systematic reviews. In particular, detailed reviews of coronary heart disease (CHD)61,62 and mental health outcomes, including depression21,63,64, in relation to work-related psychosocial exposures have been published. In these reviews, two of which include meta-analyses63,64, risk factors defined by two theoretical models of work stress, the demand-control-support model (DCS)1 and the effort-reward model (ERI)2 play a major role. A further review, which includes both prospective and cross-sectional findings, focuses on the role of work stress in relation to coronary risk factors (including hypertension, blood lipids, and metabolic syndrome)65. More specifically, Van Vegchel et al19 examine research evidence for the extrinsic (effort reward imbalance) and intrinsic (over-commitment) components of the ERI model in relation to health-related outcomes. In general, and with some significant reservations, these reviews conclude that components of DCS and ERI models are prospective risk factors for heart disease and poor mental health, particularly depression. Indeed, referring to their meta-analytic review of work-related psychosocial risk factors in relation to mental health outcomes, Stansfeld and Candy63 conclude that it provides “robust consistent evidence that (combinations of) high demands and low decision latitude and (combinations of) high efforts and low rewards are prospective risk factors for common mental disorders” (p. 443). Other authors have reviewed the effects of exposure to psychosocial risks from a wider perspective, considering both individual and environmental factors66-68. In particular, in a systematic review of prospective epidemiological data, Kuper et al.68 concluded that there was evidence for the roles of depression, lack of social support, and psychosocial work characteristics on the aetiology and prognosis of CHD, but that evidence for an effect of anxiety or Type A /hostility was less consistent. In discussing this research, Kuper et al. draw attention to the difficulty of determining the extent of bias in the reporting of psychosocial findings; they also note that bias may occur after publication as strongly positive results are more likely to be cited by other papers than weak or negative findings. In the context of the present review, it is relevant that the 71 studies of CHD (published up to 2001) summarized by Kuper et al. include almost no prospective research that examines work-related psychosocial risk factors for CHD and personality measures. Moreover, in two studies reviewed by Kuper et al. that do report both work exposures and personality characteristics, the latter are used only as control variables, the main interest being the role of psychosocial work exposures69,70. Conversely, prospective studies that focus on individual personality traits as predictors of long-term health outcomes rarely include psychosocial work exposures. Adverse health outcomes, such as all-cause mortality, cardiovascular mortality, coronary heart disease, depression and other mental health problems, suicide and attempted suicide, have been 9 linked to aspects of personality in long-term prospective studies. Thus, a 2006 review of the literature on the development and course of physical illness highlights the adverse effects of negative affectivity and anger/hostility, and the positive role of optimism29, while more recent studies identify extraversion, conscientiousness, and sense of coherence as significant predictors of favourable long-term mental and physical health outcomes30,71,72. Possible mechanisms underlying the effects of personality on long-term health include shared genetic influences, health behaviours, and the influence of personality on appraisal, coping, and physiological reactivity29; personality may also influence exposure to potential stressors (including those in the workplace) and the stressreducing resources (e.g. social support) available. One possible explanation of the relative lack of long-term prospective research that analyses both personality measures and psychosocial work exposures is that the job strain/iso-strain model1, which has attracted much research attention, only includes work environment characteristics; it does not take into account the possible role of individual differences in personality and coping in responses to adverse work conditions. Proponents of the DCS model point to evidence suggesting that individual differences are unlikely to account for the association between job strain and CHD6, although the need for further research into interactions between environmental stressors and personality characteristics is recognized. An important exception to the paucity of research combining work exposures with individual personality characteristics is a study based on data from the Whitehall II study of UK civil servants5. The analysis included measures of hostility, Type A behaviour, competitiveness, negative affectivity, minor psychiatric disorder, and two coping patterns, together with measures of job control, in relation to newly reported CHD events over a 5.3 yr follow-up period. The results showed that when age-adjusted odds ratios for the effects of low job control on CHD outcomes were compared across sub-groups identified as having or not having each negative personality characteristic, differences were small and not consistently in one direction, nor consistently in the same direction for men and women. These results were not substantially changed by including other control variables, by use of different analyses, or when job demand and social support were used as exposure measures. The authors concluded that adverse effects of low job control could not be explained by confounding effects of negative personal characteristics, or by a generalized tendency for neurotic individuals to complain. They also ruled out possible mediating or moderating effects of negative personality factors, concluding that their findings “seem to justify the relative disregard of personal factors and individual differences concerning low job control” (p. 406). However, the authors noted some psychometric problems with their measures, and suggested that other personal attributes, e.g. locus of control, or use of different work stress models, might produce different results. Moreover, this study only considered CHD outcomes, and the authors emphasised that personal characteristics should certainly not be neglected in the broader field of job stress research. 10 In contrast to the job strain model, the Effort-Reward Imbalance (ERI) model incorporates an intrinsic component, a personality characteristic designated over-commitment (OC), which reflects excessive striving combined with a strong need for approval and esteem. Studies reviewed by Van Vegchel et al.19 suggest that there is evidence for a significant additive role of OC, but there is little support for the model that predicts that OC and ERI act synergistically to predict health outcomes. The aim of the present review is to bring together findings from prospective research which examines personality factors and work-related psychosocial risks as joint predictors of mental and physical health outcomes. The review focuses on two main questions: • First, is there evidence that personality variables contribute to explaining health outcomes over and above the effects of work-related psychosocial risk factors? In this context, not only direct relationships, but also possible confounding, mediating, and/or reverse or reciprocal effects among personality variables, psychosocial risk factors, and health outcomes are potentially relevant. • Second, is there evidence that personality factors act as moderators of relations between work-related psychosocial risks and health outcomes? As described below, a systematic search of the literature published from 2000-2009 inclusive was undertaken to address these questions. 2.2 Literature search The main literature search was carried out using the ISI Web of Science, and two components of the ‘Scopus’ database ‘Health Sciences’ (which includes Medline) and ‘Social Sciences & Humanities’ (which covers journals in Psychology and Social Sciences). Additional searches were carried out using OvidSP. Further material was found by examining journal articles listed as having cited the articles located in these searches. The search terms identified prospective/longitudinal studies published in peer-reviewed journals in the years 2000-2009, in which measures of work-related psychosocial risks, including (but not restricted to) dimensions from the Demand-Control-Support (DCS) model and the Effort-Reward Imbalance (ERI) model, together with one or more personality measures, were used to predict health-related outcomes. Search terms for personality included specific personality variables in addition to the general terms ‘personality’, disposition*, and trait*. The main search terms used are shown in Table 2.1. 2.2.1 Criteria for selecting studies The many documents located in these searches were examined to identify studies that met pre-determined criteria, specified with reference to recent systematic reviews of psychosocial risk factors in relation to health outcomes63,64,68. 11 Table 2.1 Main terms used in the literature search Personality Personality Disposition* Trait* Vulnerable / vulnerability Resilient / resilience Negative affect* Positive affect* Neuroticism Extraversion Optimism Locus of control (LOC) Self-efficacy Sense of coherence (SOC) Hostility Type A Over-commitment (OC) Coping resources NEO inventory NEO-FFI Outcomes Mortality Cardiovascular Heart disease Coronary Psychiatric Mental health Distress Anxiety Depression Mood Affect* Psychosomatic Somatic symptoms Well-being Job satisfaction Illness Sickness absence Sick leave Turnover Psychosocial work environment (Work* OR job OR occupation*) AND (stress OR psychosocial) AND Method Demand* Control Discretion OR decision authority OR decision latitude OR autonomy Social support Iso-strain OR job strain Effort AND reward Organizational injustice Organizational justice Work hours OR time pressure Workload Job security OR job insecurity Re-structuring OR down-sizing OR relocation Longitudinal* Prospective* Follow-up Search terms in different groups were joined by AND, and those within groups by OR The following criteria were applied in selecting the studies to be included: • Longitudinal studies of working age adults which included one or more psychosocial work exposures AND one or more personality characteristics as predictors of health-related outcomes. 12 • • • • • • • • Outcomes were cardiovascular disease, psychiatric diagnoses, mental and physical health, psychosomatic complaints, insomnia, job-related affective responses, and job-related behavioural outcomes (e.g. sickness absence, turnover), identified by hospital or company records, assessed by formal diagnostic interview, or by referenced self-report scales. Clear descriptions of the measures used. A follow-up period of at least one year Control for initial level of dependent measure, and/or exclusion of baseline ‘cases’. A study size of at least 200 participants Sample located in Europe, North America, New Zealand, Australia, Japan or Russia English language articles published in peer-reviewed journals, 2000-2009 Must report statistical results relating to personality variables (i.e. not simply state that they were used as controls) A total of 33 studies met the criteria and were included in the present review; the relatively small number of studies selected was primarily due to the triple requirement for prospective data in which both personality and psychosocial risk exposures were assessed. As others have noted73, the majority of studies in this research area are either crosssectional and/or do not include measures of both personality and work characteristics. 2.3 Results Details of the 33 studies included in the review are summarized in Table 2.2 (pages 2638). The follow-up durations generally ranged from 1-10 years, although two studies used childhood measures. Both men and women were included in almost all the studies, but separate results were not always presented; more usually, gender was treated as a control variable. The analysis methods included multiple regression and structural modelling (with continuous variables) and, more frequently, logistic regression models (based on groups with different levels of exposure). The psychosocial exposure measures and types of outcome variables used are outlined below. The personality variables, their main effects on outcome measures, and interactions between personality and psychosocial risks, are then examined in more detail. 2.3.1 Psychosocial work exposures Almost half the studies reviewed used measure from (or conceptually similar to) the DCS model or the ERI model to assess psychosocial work exposures. DCS model. Ten studies used measures of work-related psychosocial exposures derived directly from the DCS model, or based on similar constructs [6, 7, 8, 10, 12, 16, 19, 21, a 32, 33] . Most of these studies assessed job demand, control, and social support, although a The numbers in square brackets in the text identify the studies summarised in Table 2.2 13 in some cases only two of the three measures were used. If only one of the three DCS measures was used, the study was included in the ‘other exposures’ group. ERI model. Five studies included in the review were based on the ERI model [1, 2, 4, 9, 31]. All of these studies assessed effort, reward and effort/reward imbalance, although proxy measures were used in some instances, e.g. [31]. Each of these studies assessed the intrinsic effort component of the ERI model, over-commitment (OC), but only two studies [2, 31] tested the OC x ERI interaction. DCS and ERI models. Three studies [11, 13, 29] used both ERI and DCS measures. Other exposure measures. Non-theoretically based measures were used to assess work exposures in 15 studies; these studies were more heterogeneous than those based on the DCS or ERI models. Some focused specifically on a single exposure measure, assessed subjectively, e.g. job control [15] or objectively, e.g. unemployment [5]; others used objective and subjective assessments of the same work exposure [3]. In some studies, specific objective work events were assessed in addition to a general perceived work stress measure [e.g. 14]. One study based on the ‘Organizational Justice’ model [27] used measures of relational justice and procedural justice as exposure measures. 2.3.2 Outcome variables Overall, half the studies used only one outcome measure, although those that assessed jobrelated affective responses tended to use several measure, e.g. scales from the Maslach Burnout Inventory (MBI). Four different types of outcome variables were identified in the studies reviewed. General mental health outcomes [1] to [15]. The mental health outcomes assessed in these studies included general measures of mental health/psychological distress, specific measures of depression and/or anxiety, self-reported health, and insomnia. In most cases, outcomes were assessed by standard self-report scales, but in two studies [6, 7] by interviews carried out either face-to-face or by telephone. Job-related affective well-being [16] to [25]. Six studies in this group used scales from the Maslach Burnout Inventory (MBI)74, sometimes coupled with more general measures (e.g. fatigue), for assessing outcome [16, 17, 18, 20, 22, 24]. Participants in these studies were primarily teachers, healthcare workers, and other human services personnel, although three studies [18, 20, 25] were based on random samples of the general population (screened to include only employed individuals) or trades unions. The majority of the studies used non-theoretical measures to assess work characteristics, but three studies used measures from the DCS model [16, 19, 21]. Behavioural outcomes [26] to [30]. Of the five studies that used behavioural measures, four derived the outcome data from formal organizational records relating to sickness absence rates [27, 30]; health-care usage [28] and physician visits [29]. Self-reported voluntary job turnover was used as the outcome in the remaining study [26]. One study 14 [29] included measures from both the DCS and the ERI models, and one used measures of organizational justice [27]; in the remaining three studies, non-theoretically based measures (down-sizing, stressful work events, and work challenge/hindrance stress) were used [26, 28, 30]. Cardiovascular disease outcomes. [31] to [33]. The three studies in this group analysed longitudinal data from the Whitehall II prospective study of UK civil servants; in each case the mean follow-up period was approximately 11-12 yrs. Of the three studies, one study [31] used proxy measures of effort, reward, and OC to test the ERI model, while two studies [32, 33] used measures from the DCS model of work stress. 2.3.3 Personality variables used in the studies The majority of the studies reviewed assessed only one or two personality characteristics (20 studies reported one personality measure, and 5 studies reported two measures). In all, there were 56 instances in which personality measures were analysed in relation to one or more outcome variables. The personality variables most frequently reported were the OC component of the ERI model and neuroticism/NA, but three other personality measures (hostility/Type A, locus of control/hardiness, and sense of coherence) were each used in at least five of the 33 studies, although not always assessed by the same scales. Of the remaining 11 measures, 7 were used in only one study. Information about the main and interactive effects of the personality variables is summarised in Table 2.2. The statistical data are taken from the fully adjusted models, although several studies noted the problem of possible over-adjustment, e.g. by including as control variables, health behaviours and/or lifestyle variables which may act as mediators of relations between personality/psychosocial factors, and health outcomes. Additive effects and, if reported, tests of the moderating effects of personality on relations between psychosocial work exposures and outcomes are shown, together with notes on confounding or mediating effects. 12 of the studies reviewed reported testing interactions between personality and work exposures but, in several cases, only limited details were provided. Findings for each of the main personality measures used are reported below. 2.4 Findings for individual personality characteristics 2.4.1 Over-commitment (OC) The personality characteristic of over-commitment describes individual attitudes, behaviours and emotions reflecting excessive work-related striving combined with a need for approval and esteem. The measure forms an integral part of the Effort-Reward Imbalance (ERI) model75. A recent psychometric evaluation demonstrated that the current version of the OC measure and the other ERI scales have stable psychometric properties76. 15 Main effects. Eight of the studies included a measure of OC, together with the effort and reward measures from the ERI model; three of these studies also used DCS measures. None of the studies that used an OC measure used any other personality measures. OC showed significant main effects, additively with ERI measures, in all except one of the studies [29]. Among men, high OC was consistently predictive of adverse health-related outcomes, including psychological ‘caseness’[1], self-reported depression, anxiety, and/or somatic symptoms [2, 4], insomnia [11], poor subjective health ratings [9], and incident CHD [31]. Risk ratios (if reported) were generally in the ‘moderate’ range, 1.5 - 2.0, except for CHD for which the HR value for OC was 1.26 (CI 1.09-1.46). Among women, the effects of OC were less consistent; for instance, OC did not predict subjective health ratings among women [9], nor was it a predictor of anxiety or somatic symptoms, although it did predict depression in women [4]. Findings from one study suggested that high OC was a risk factor for professionals, but not for manual workers [13]. Entirely non-significant findings for the main effects of OC were reported in only one study. In this case, separate components of the ERI model (but not OC or effortreward imbalance) were significant predictors of an objective measure of health care usage [29]. Thus, the strongest results for OC as a psychosocial risk factor were found for men in relation to a range of health-related outcomes, primarily of a psychological or psychosomatic nature. Interactive effects. Although the ERI model includes predicted interactions between OC and effort-reward imbalance, only two out of the eight studies that used the OC measure reported testing OC x ERI interactions. In both cases [2, 31], the results were nonsignificant. The present review therefore provides no evidence that OC acts as a moderator of ERI effects in relation to mental health outcomes or incident coronary heart disease, thus contributing further non-significant results to the generally inconsistent evidence reviewed by Van Vegchel et al.19. However, the failure to report tests of interactions in six of the studies concerned weakens any wider conclusions that can be drawn. Differences between men and women in the extent to which OC acts as a risk factor for adverse health outcomes suggest that interactions between gender and OC might contribute significantly explaining outcome variance. 2.4.2 Neuroticism / negative affectivity (NA) NA is used here to refer to both neuroticism and negative affectivity, both of which reflect emotional vulnerability, pessimism, and a general disposition to react negatively to life and work stressors; individuals high in NA tend to be anxious, easily upset, often moody or depressed, and focused on negative aspects of self, other people and the world in general. In the studies reviewed, NA was the most frequently reported personality characteristic; it was assessed in 11 of the 33 studies, distributed across all the four types of outcome variables. Five of the studies based on the DCS model and six of the non-theoretically based studies included NA, although none of the ERI studies did so. In six of the studies that used a measure of NA, other aspects of personality were also assessed. NA is often 16 regarded as a confounding variable in the link between psychosocial work stressors and health outcomes, and several noted that it was included for that reason [3, 7, 8]. Main effects. In 9 out the 11 studies, including all the DCS studies, NA was a significant risk factor in multivariate predictive models, particularly in relation to mental health outcomes [3, 7, 8, 14], but also for job-related affective outcomes [16, 23], and for CHD [32, 33]. Risk ratios for NA in relation to mental health outcomes were reported for two studies; the values were 1.98 (1.66–2.36) men / 1.55(1.33–1.81) women [7], and 3.59 (2.06–6.26) men/women [14], representing moderate to strong associations. NA was also found to be a significant risk factor for sickness absence in both men and women [27], but it was not related to voluntary job turnover [26]. In the two studies of CHD incidence [32, 33], NA was a main focus of interest rather than being included only as a potential confounder. Adjusted for demographic factors, those in the highest NA tertile (top one-third of scores) were at significant, albeit not large, risk for incident CHD events, hazard ratio=1.32 (1.09 - 1.60); controlling for job strain, health behaviours, and other potential confounders in the multivariate model had little effect on this finding [32]. However, the positive dispositional counterpart of NA, positive affectivity (PA) did not show significant effects, nor did the ‘affect balance’ score (the difference between PA and NA scores). A further study of NA in relation to CHD [33], based on a similar Whitehall II dataset, used the ‘Relative Index of Inequality’ (RII) as the risk index. The RII represents the hazard ratio for the extremes of the observed score distribution. In this study the RII value for NA was 1.64 (1.17 – 2.32). NA and inflammatory biomarkers were found to be independent predictors of incident CHD; there was no evidence of mediation effects. Confounding effects of NA. Three studies of mental health outcomes [3, 7, 8] explicitly noted the role of NA as a potential confounder of relations between psychosocial factors and mental health outcomes and reported the significance of NA as a main effect, but only one study reported data showing the effects of controlling for NA. In this study [7], the effects of high job demand (highest tertile scores) remained significant when NA was included in the multivariate model, and the reduction in RR values was small for both men and women. Interactive effects of NA. Two very different studies [16, 27] included tests of interactions between NA and psychosocial risk factors in predicting outcomes; both reported significant findings. Elovainio et al.77 [27] examined the roles of NA and hostility as moderators of relations between measures of organizational justice and sickness absence rates. In addition to a significant main effect of NA in both men and women, NA moderated the effect of relational justice on sickness absence rates among men, but not among women. Thus, consistent with a personality vulnerability model, the combination of a stressful psychosocial context (low relational justice) and high NA among men led to particularly high rates of absence. 17 Houkes et al.78 [16] used LISREL structural modelling to evaluate additive and interactive effects of NA in a cross-lagged panel design. In the additive model, inclusion of a direct causal path from Time 1 NA to Time 2 emotional exhaustion significantly improved the fit of the synchronous model; however, reverse causal and reciprocal paths were not significant. Interactive effects were evaluated by sub-group analyses; a significant moderating effect of NA on relations between workload and exhaustion was found. The total effect of Time 1 workload on Time 2 emotional exhaustion was .06 in the low NA group and .27 in the high NA group. This analysis confirmed and extended previous findings56, and illustrated one of the substantive mechanisms identified by Spector et al.34. In summary, NA was found to act as a significant additive risk factor in almost all the studies in which it was included, but there was little evidence of it acting as a confounding variable. There was also no evidence of reversed causal effects from psychosocial stressors to NA measures, or of reciprocal effects, although these were tested in only one study [16]. Significant interactive effects were found in two studies [16, 27] both of which were consistent with a vulnerability model of NA. 2.4.3 Hostility / Type A behaviour Main effects of hostility /Type A behaviour. Although both hostility and Type A behaviour pattern have been linked with the incidence of cardiovascular disease79,80, in the studies reviewed, these personality characteristics were assessed in relation to mental health and behavioural outcomes. Measures of Type A behaviour [20, 28], and hostility [27, 30] were each reported in two studies; in addition, one study [12] assessed both these characteristics, and one study used teacher ratings of hostility at age 8 yrs to predict adult health outcomes in relation to employment status [5]. A significant effect of hostility was found in both the studies that used sickness absence as an outcome measure. In one study, the risk of absence was higher by a factor of 1.2–1.4 among individuals high in hostility than among others [30]. Similarly, the second study reported significant regression coefficients for hostility as a predictor of sickness absence in both men (.15*) and women (.03**) [27]. Hostility, but not Type A, predicted increased depression over a 3-yr follow-up in a large French cohort [12]. Type A was also nonsignificant in relation to health care usage [28], and in an exploratory path analysis in which job demand and workload, and several personality measures, were used to predict fatigue and exhaustion [20]. Confounding/mediating effects of hostility/Type A behaviour. There was no evidence in these studies that hostility or Type A acted as confounding variables in relations between psychosocial factors and health outcomes, or that its effects on outcome measures were mediated by psychosocial factors. Interactive effect of hostility/Type A behaviour pattern. Three studies tested hypothesised interactions between psychosocial risk factors and hostility [5, 27, 30]. In each case, the predicted interactions were significant; high hostility was a risk factor for individuals experiencing stressful conditions, specifically, unemployment [5], low job control during 18 organizational down-sizing [30], or lack of procedural justice [27], although in two cases the findings applied only to men [5, 27]. In addition, one study tested multiple interactions on an exploratory basis [12]; hostility was a component of one of the significant interactions found. 2.4.4 Locus of control / hardiness Locus of control (LOC) measures assess the extent to which individuals believe that outcomes are determined by personal effort and ability rather than by external influences such as fate, chance and powerful others81-83. Locus of control, considered together with hardiness (a composite measure in which LOC is the major component84) was used in five studies [6, 15, 20, 21, 28]. These studies reported very diverse findings, specifically, a significant negative main effect of internal LOC on incidence of depression in a large sample of Canadian employees [6]; non-significant results for the main effect of hardiness on health-care usage [28]; moderator effects of LOC on relations between DCS dimensions and job dissatisfaction [21]; a significant negative effect of hardiness on emotional exhaustion in a causal model [20]; and a significant path by which personal control mediated the effect of work control on health over a 10-yr follow-up period [15]. Main effects. Findings from two studies [6, 20] pointed to additive roles for LOC and hardiness, respectively, in attenuating negative affective states associated with psychosocial exposures; in two other studies [15, 21] tests of meditation and moderation rather than possible additive effects were the main focus. Confounding. One study [6] noted that inclusion of personality variables in the regression model reduced the effect of work demand to non-significance; this effect appeared to be due to the effects of two personality variables, locus of control and sense of cohesion, acting either as confounders or mediators. Personal control (LOC) as mediator. Latent growth curve modelling was used to evaluate the roles of work control and personal control (similar to LOC) in predicting health outcomes in a 10-yr follow-up study of men employed in a rural U.S. state85 [15]. The final model demonstrated an indirect influence of work control on the two health outcomes; the effects of initial level of work control and subsequent change in work control on health at follow-up were fully mediated through the corresponding initial level and changes in level of personal control. The findings suggest that personal control can be influenced by work experiences, and that change in personal control has a long-term impact on health, although no reverse causal paths were tested. Moderating effects of locus of control. Significant moderating effects of LOC in relation to the exposure measures of the DCS model were demonstrated in one study [21]. In data collected over a 2 yr follow-up period, a significant four-way interaction was found; job demand and control interacted to predict job dissatisfaction only for internal locus of control participants under conditions of high social support. However, the form of the interaction was not readily interpretable, and the interaction term accounted for only a very small proportion of variance in the final model. 19 2.4.5 Sense of Coherence (SOC) Individuals high in SOC view their environment as manageable and comprehensible; they are more likely to perceive themselves as able to adapt to the demands they experience, less vulnerable to stress, and more able to maintain health42. SOC is highly negatively correlated with NA86 and would therefore be expected to have favourable effects in attenuating or moderating relations between work-related psychosocial risks and health measures. Five of the studies reviewed used a measure of SOC, in relation to measures of general mental health [6, 8, 10] or job-related affective outcomes [24, 25]. Main effects of SOC. Two studies found significant negative relationships of SOC with measures of mental health in multivariate models including psychosocial risk factors and confounding variables [6, 8]. SOC was also included in a causal model of relations between psychosocial work dimensions and four measures of job-related affective wellbeing [25]. There was no significant path between SOC and T2 affective responses, although one reverse causal path from a T1 affective measure to T2 organizational climate was found. SOC as a mediator. In a best-fit structural model, SOC acted as a mediator of the effects of organizational climate and job insecurity on emotional exhaustion and psychosomatic symptoms; also, change in SOC mediated the effect of change in organizational climate on change in both indicators of well-being [24]. SOC as moderator. Moderating effects of SOC were found in one study [10]; under conditions of high job strain, high SOC increased the probability of ‘excellent’ SRH ratings (OR=2.35**), and reduced the probability of musculoskeletal pain (OR=.34**). 2.4.6 Other personality variables The main findings for other personality variables used in the studies reviewed are summarised below. • • • • • Four studies included extraversion [14, 20, 23, 26] but it was significant only in relation to voluntary job turnover [26]. Positive affectivity (PA), which is closely linked to extraversion, was non-significant in relation to incident CHD [32]. Low self-esteem was a risk factor for increase in depression [12]; it was also negatively related to mental distress and emotional exhaustion in men but not women [18]. It was non-significant in two other studies [6, 19]. Conscientiousness was used in two studies [20, 26,] as part of the Five-Factor Personality Inventory87. It was not significant in either study. Self-efficacy was also used in two studies. In one study [22] it was a significant predictor of burnout, the path being mediated by work stress. In the other study [17], it was a direct predictor of client engagement (the reverse of burnout). Other personality measures, including optimism (significantly negatively related to job-related affective distress among men [18]), and openness (non-significant in relation to onset of depression [14]) were each used only in a single study. 20 2.5 Conclusions The findings outlined above demonstrate that personality is implicated in several different ways in work stress processes. Thus, the effects of work-related psychosocial stressors on health may be independent of personality; they may be confounded by personality; they may be moderated by personality; or they may mediate the effects of personality. These and other more complex relationships (including reverse causation and reciprocal effects) were potentially within the scope of the present review. However, although additive effects were tested in almost every study, some important mechanisms were evaluated only in relatively few of the studies concerned. In particular, in spite of the potential importance of moderator effects in stress processes, only 12 out of the 33 studies (36.4%) reported tests of interactions between psychosocial stressors and personality. This proportion agrees closely with findings from a systematic review of multivariate analyses in 56 papers published in 2002, in which self-reported health was the outcome variable and which met other specified criteria88. Failure to report tests of interactions was the most common problem identified; it applied to 63% of the studies examined, a proportion virtually identical to that found in the present review. Thus, almost two thirds of the studies considered here did not test any hypotheses predicting interactions between personality and psychosocial stressors, or even evaluate possible interactions on an exploratory basis (or, if such tests were carried out, they were not reported). In the majority of the studies reviewed, therefore, the idea that personality characteristics may make individuals more vulnerable to, or more resistant to, the adverse effects of psychosocial stressors was apparently not addressed. This finding is surprising as several of the personality variables concerned (e.g. NA, locus of control, sense of coherence) have been shown to act as moderators of relations between psychosocial stressors and health outcomes37,56,58,89,90. Failure to consider possible interactions can lead to potentially significant and revealing moderating effects remaining concealed, while weak and/or non-significant main effects are reported. This problem is especially relevant in relation to ‘cross-over’ interactions in which the main effects of both interacting variables may be non-significant. It is also noteworthy that in the relatively few studies in which moderating effects were reported, the majority (75%) found significant results for one or more interactions. It is possible that this finding reflects a reporting bias, that is, the tendency for significant findings to be reported while non-significant findings are disregarded. Moreover, two of the three studies that reported non-significant interactions were based on the ERI model in which OC, regarded as an intrinsic personality moderator variable, is an inherent component, thus making it more likely that interactions will be tested and reported, even if non-significant. An additional problem in drawing general conclusions from the present review was that the 33 studies that met the selection criteria proved to be very heterogeneous, ranging from epidemiological research primarily concerned with identifying psychosocial risk factors in large population samples to studies that used structural models to evaluate the 21 magnitude and direction of causal pathways among measures of personality, psychosocial stressors, and health in particular employee groups. A marked feature of the epidemiological research was the tendency to dichotomise (or otherwise sub-divide) continuous variables, thus losing information from the original scales. Also, epidemiological studies were more likely to present separate data analyses for men and women, rather than to treat gender, and interactions with gender, as factors in a multivariate model. Although all the studies were prospective with initial baseline data collection and one or more follow-up assessments, they also varied widely in the nature and size of the samples, the follow-up duration, the number of waves of data collection, the psychosocial measures used, and the types of outcomes assessed. These differences in research aims and methodology limit direct comparisons across studies. Instead, as a framework for drawing together the main findings from the review as a whole, a series of general questions is considered below with reference to the findings of the papers reviewed. 2.5.1 Do personality characteristics act as independent risk factors? This question addresses the issue of the independent additive effects of personality and work-related psychosocial factors on mental and physical health. Two personality variables identified in the present review, over-commitment (OC) and neuroticism (NA) stood out as being significant, consistent, and moderately strong risk factors for adverse mental health and job-related affective outcomes, and significant (although smaller) risk factors for CHD incidence. NA was a significant predictor in 9 of the 11 studies in which it was assessed, while OC was significant in 7 out of 8 studies. Independently of psychosocial exposures, NA was a significant predictor not only for selfreported mental health, job-related distress and incident CHD but also, among women, for objectively recorded sickness absences. Thus, as a risk factor, the independent effects of NA were apparent in relation to psychosocial risk factors represented in the DCS model, and a range of non-theoretically based measures, and in relation to each different type of health outcome. The finding that NA is associated with a range of adverse health effects in a variety of different contexts, is consistent with evidence summarised in a recent review article91. This article describes the many mental and physical health disorders, the impaired quality of life, and the high usage of health care services, associated with high NA. The author concludes that there is ‘growing evidence that neuroticism is a psychological trait of profound public health significance’91, and recommends that understanding the nature and origins of neuroticism, and the mechanisms which link it to mental and physical disorders, should be a research priority. In the studies reviewed, the OC measure was used primarily in relation to general mental health and cardiovascular disease outcomes; in each of these studies, OC was a significant independent predictor in multivariate analyses including psychosocial work exposures 22 (ERI measures). In addition, one study reported non-significant effects of OC in relation to objective measures of physician visits. However, none of the studies included measures of both NA and OC; thus, the extent to which NA and OC contribute independently to observed outcomes when both measures are included in the predictive model could not be established. Evidence from two cross-sectional studies92,93 suggests that NA and OC are significantly correlated, and that if both NA and OC are included in multivariate models predicting health outcomes, the magnitude of the effect of OC is reduced, in some cases, to non-significance, while NA remains significant. Whilst findings for other personality variables considered in the present review were less clear than those for NA and OC, three other measures (hostility/Type A, locus of control, and sense of coherence), each used in at least five of the studies concerned, also contributed additively to multivariate models. In particular, ‘sense of coherence’ (SOC) which is conceptualised as a positive personality resource associated with adaptive coping behaviours, was a significant predictor of favourable health outcomes in two studies. Hostility showed significant and adverse main effects in four studies, but it also interacted with psychosocial work dimensions to predict outcomes. 2.5.2 Do personality measures act as confounding variables? There was little evidence to suggest that personality variables acted as confounders of relations between work-related psychosocial factors and health outcomes. In one study, control for personality variables reduced the effects of work demand to non-significance, but other studies specifically noted the absence of personality confounding effects. It is relevant that the studies reviewed included control for the baseline level of the dependent variable, and some screened baseline ‘cases’ out of the analysis sample. Consequently, variance associated with personality and other confounding factors would be largely accounted for by the dependent variable as assessed at baseline, thereby reducing potential confounding effects in longitudinal analyses. Thus, although NA tends to act as a confounding variable in cross-sectional studies of psychosocial stressors, particularly in relation to self-reported health outcomes94, in the prospective studies reviewed here, confounding effects of NA were not markedly apparent. 2.5.3 Does personality moderate relations between psychosocial stressors and health? In the 12 studies that tested interactions between personality and psychosocial stressors, hostility stood out as showing the most consistent moderating effects. Thus, in significant interactions, hostility was a risk factor for poor self-rated health among unemployed, but not employed, men; it interacted with procedural justice to predict sickness absence, but only among men; and, during a period of down-sizing, it interacted with job control, also to predict sickness absence. In addition, in an exploratory test of multiple interactions, hostility interacted with job control; high-hostile men appeared to benefit more from high job control (in terms of reduced depression) than low-hostile men. 23 These findings highlight the particularly adverse effects observed when high hostile individuals are exposed to stressful work conditions, including job insecurity or actual job loss, lack of procedural justice at work (i.e. lack of fairness in organizational policies and practices), and low control at work. It is also noteworthy that the present review included only two studies in which sickness absence was the outcome measure, and in both these studies, hostility moderated the effect of work conditions on absence. It is possible that high hostility leads to lack of work-related social support, and difficult interpersonal relations with co-workers, accentuating negative responses to stressful conditions, including withdrawal from the work situation. NA was found to be a significant moderating factor in two studies, both of which showed that high NA individuals were more vulnerable to work-related stressors (high workload in one study and, in the other, lack of relational justice, among men). Although interactions were also reported in other studies (e.g. SOC moderated the effects of high strain conditions on health outcomes; LOC moderated the effects of iso-strain on job dissatisfaction; and self-efficacy moderated the effects of role ambiguity and workload on job satisfaction), only for NA and hostility was there evidence from more than one study of significant findings for predicted interactive effects. The small number of studies that tested interactions precluded identification of particular psychosocial stressors and personality variables that combine synergistically to predict specific types of outcomes. The practical implication of interactions between psychosocial risk factors and personality, as noted by Houkes et al.78, is that organizations wishing to reduce ill-health and distress among employees should consider both work characteristics and individual factors. A similar conclusion was reached by Ferguson et al.73 from meta-analytic structural equation modelling of ‘perceived negative job characteristics’ (PNJC) and ‘negatively oriented personality’ (NOP) as predictors of concurrent and future symptom reporting in longitudinal studies. In this meta-analysis, it was found that a model based solely on NOP offered a more parsimonious account of baseline and future symptom reporting than did PNJC. In view of the importance of NOP, the authors concluded that interventions should focus on individuals and organizations, rather than targeting interventions solely at the organizational level. 2.5.4 Are the effects of personality mediated through psychosocial stressors? Three studies examined mediating effects using structural modelling analyses. In one of these studies, a general measure of work stress was found to mediate the path between the personality measure of self-efficacy and the health measure of burnout39; thus, in this model, self-efficacy influenced perceptions of work stress which in turn influenced burnout. This path represents the ‘normal’ theoretically predicted causal direction in which a personality trait influences work perceptions, which in turn influence health. There was no evidence of reverse causation in this analysis. In contrast, no support for the ‘normal’ causal direction was reported by Mäkikangas et al.95; rather one reverse causal path was 24 found in which affective response at follow-up predicted baseline organizational climate. Also, in this study, SOC did not act as a mediator. Two other studies of mediation adopted a different model, in which the personality variable was treated as the mediator between psychosocial stressors and health. First, over a one-year period, a good organizational climate and low job insecurity at Time 1 was positively related to high levels of SOC, which in turn predicted affective well-being at Time 243; in this study, changes in organizational climate were related to changes in wellbeing through changes in SOC. Second, also using latent growth curve modelling, the effects of level and change in job control on health measures over a ten-year period were found to be mediated by level and change in personal control (a measure of LOC)85. Both these studies demonstrated that personality measures changed in response to changing work conditions. Whilst measures of personality would normally be regarded as relatively stable, individual levels of SOC42 are considered to be malleable and shaped not only by early childhood but also by adult work and life experiences43. The role of SOC as a mediator variable is consistent with this interpretation. In this case, work experiences gave rise to change in SOC over a time period of only one year, which accords with findings suggesting that the SOC measure has a significant state component96, rather than representing a stable global orientation. Evidence that personal control (LOC) acted as a mediator variable related to a longer time period (10 years)85 but similar arguments apply, and are consistent with earlier findings suggesting that LOC is reciprocally related to work conditions97,98. 2.5.5 Implications Several general conclusions can be drawn from the results outlined above. First, it is clear that personality plays significant roles in the paths by which work-related psychosocial stressors are associated with adverse mental and physical health outcomes, although findings across different studies are not entirely consistent. Second, these paths are not necessarily in the theoretically-predicted directions, nor are they necessarily unidirectional, although the relatively small sample of studies reviewed does not allow clear conclusions about the relative importance of the different mechanisms. Third, the findings tentatively suggest that different personality traits may act through different pathways. For instance, negative affectivity and over-commitment showed strong additive effects, largely independent of work-related psychosocial risks, hostility acted as a vulnerability factor interacting with psychosocial risks, and mediator or mediated effects were most apparent for the dimensions of locus of control and sense of coherence. However, any such conclusions must be qualified by the fact that in many studies only additive effects were considered, and thus more complex mechanisms may have been overlooked. The relevance of examining the various mechanisms by which personality is implicated in work stress processes depends on the focus, aims and methods of any particular study. However, it is clear that the importance of possible interactive effects has been disregarded in much research. In particular, interactions reveal ways in which a particular 25 personality trait coupled with a particular psychosocial work exposure may lead to poor mental or physical health while either factor alone would not have done so. Such information can potentially guide more effective intervention strategies to enhance wellbeing at work. From both research and applied viewpoints, it would be valuable if future research gave greater attention to predicting and testing interactive effects, using appropriate statistical methods, and reporting the findings irrespective of whether or not they are significant. Prospective studies of mediating effects, and particularly the possible role of psychosocial work exposures in bringing about changes in personality, would also contribute to a better understanding of work stress processes. Issues such as these have been widely recognized in the research literature. For instance, it has been suggested that one reason the success of organisational attempts to modify job strain have so far been relatively modest may be that the effects of personality are largely ignored when work stress is considered to originate mainly from work conditions99. Similarly, Wilhelm et al.100 note the need for “more longitudinal studies and consideration of factors which the worker brings to the workplace (psychosocial issues, personality traits), as well as interpersonal issues and consideration of systemic, organizational, political and economic factors, including leadership styles”. Other researchers have also recommended that more attention be given to personality in work stress research89,101-103. More generally, over the past two decades, industrial changes (including organizational restructuring, down-sizing, privatisation, out-sourcing and contract work) associated with economic globalisation have increased job insecurity and led to changes in work processes and management behaviour. Such changes may adversely affect employees; for instance, in a recent survey, 85% of the 86 studies examined reported adverse health and safety effects of down-sizing104. These changes in work conditions have led to recognition of the need to expand traditional work stress models to include new work dimensions, such as employment uncertainty, irregular/atypical schedules, emotional work demands, and the quality of social relationships at work105. Innovative models which incorporate not only novel work dimensions but also take into account the role of personality in coping and adaptation are needed to fully address these concerns. 26 Table 2.2 Summary table of the 33 studies reviewed Author Sample Follow-up duration Dependent measure (s) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Personality measures Confounding /control variables included in analysis model Main effects of personality Tests of personality x psychosocial work factors interactions reported ? Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects MENTAL HEALTH OUTCOMES Bridger et al (2009) 791 UK naval personnel 319 females 472 males 1 yr 3 waves of data collection Strain defined as GHQ-12 ‘caseness’, cut point ≥ 4 Chronic strain group (‘cases’ at each assessment, n=78), compared with ‘strainfree’ group (n=345) Effort/reward (ERI measures) Overcommitment (OC) Anxiety and depression (HADS scales) Life satisfaction Yes Work hours Overcommitment (OC) 1 BuddebergFischer et al (2008) 433 Swiss medical residents (physicians) 2 yrs (T2 and T3 from prospective study) 2 Burgard et al (2009) Good study 3 Two samples of employed U.S. adults N= 1507 age 25+ yr 1986-1989 N=1216, age 25-74 yrs 1995-2005 3 / 10 yrs 2 waves of data collection ERI measures of effort and reward Physical/mental well-being Self-rated health (SRH) Depressive symptoms Telephone interview assessments Yes Perceived job insecurity Objective job insecurity (actual experience of unemployment for one yr prior to each data collection wave Neuroticism Over-commitment: (β=.32***), and ERI (β=.19*) were both significant in the logistic model. Gender Self-reported health at baseline Gender, age, race, employment history, education, income, blood pressure, etc Significant additive effects of ERI and OC on health outcomes (p<.0001) In adjusted model, neuroticism was a risk factor for SRH B= -0.076 ** (s.e. 0.026); and for depressive symptoms B=0.067 *** (s.e. 0.012) Persistent perceived job insecurity was a risk factor for poor SRH (2 samples) and depression (1 sample) No ___ Yes ☺☺ ERI x OC interactions were non-significant for all health outcome measures No _____ 27 Author Godin et al (2005) Sample 1986 Employees from four Belgium companies Follow-up duration 1 yr Dependent measure (s) Depression Anxiety Somatisation (Symptom Check List SCL90) Chronic fatigue Drug use Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Participants with mental health problems at Time 1 were excluded, reducing the analysis sample by 25% ERI measures of effort and reward Personality measures Overcommitment (OC) Confounding /control variables included in analysis model Main effects of personality Age Education Threat from global economy Job dissatisfaction Workplace instability In men, high OC predicted three outcomes, over and above ERI: 4 Kivimaki et al (2003) Tests of personality x psychosocial work factors interactions reported ? No N=311, cohort born in1959 87% response at follow-up 27 yrs Self-rated health (5=very good to 1=very poor) n/a Employment status Unemployed vs. not unemployed at age 36 yrs Hostility (rated by teacher at age 8 yrs) Parental SES Current financial strain Alcohol use Main effects of hostility and unemployment on health were nonsignificant Yes 6,359 employees working at least 15 hrs per week Mean age 37 yrs at baseline 7 yrs; First episode of psychological distress (Composite International Diagnostic Interview) Yes Skill utilisation Decision authority Physical and psychological demands Social support, Job insecurity Self-esteem (Rosenberg scale) Internal locus of control (LOC) (Pearlin & Schooler) SOC (Antonovsky) Age and gender Family characteristics Lifestyle factors Childhood stressful events Social network In adjusted model: LOC (β=-.069**) OR = .93**(.91-.96) Yes 6 4 cycles of assessment Response rates 8586% at each cycle hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects ___ Depression OR=2.4(1.4–4.1) Anxiety OR=2.5 (1.5–4.4) Somatisation OR= 1.8 (1.1–3.1) In women, OC only predicted depression OR=1.8 (1.0–3.0) 5 Marchand et al (2005) Significant interactions between personality x work factors ☺☺ indicates initial SOC (β=-.065**) OR= .94 (.93-.95) Self-esteem (β= -.015, ns) OR = .99 (.95-1.02) Control for personality reduced the effects of work demands to ns ☺☺ Significant interaction between hostility and employment status in men (β= -0.21, p< 0.04), but not among women. Unemployment was a health risk only among men high in hostility. ☺ None significant; details not reported Non-linear relationships of work exposures with outcome were also nonsignificant 28 Author Melchior et al (2007) Sample Follow-up duration Dependent measure (s) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Personality measures Confounding /control variables included in analysis model 891 men and women (NZ birth cohort) assessed every 2 yrs from age 3 yrs. In employment at age 32yrs (response rate, 96%) Baseline psychiatric assessment, ages 11 yrs Major depressive disorder (MDD) or generalized anxiety disorder (GAD) assessed by Diagnostic Interview Schedule, and diagnosed according to DSM-IV criteria Only new onset cases included. Participants with prior psychiatric diagnosis were excluded DCS model: Job demands Work decision latitude Social support Physical job demands NA (rated by interviewer from Big Five Inventory items) SES Internalizing/ externalizing disorders, age 11 yrs Work decision latitude Social support Physical job demands 1392 Japanese civil servants 1 yr Subjective perceptions of quality of life in four domains: Baseline measures included in the analysis model Karasek job strain measures Job demand Job control SOC 13-item translated version Gender Age Employment category 7 Nasermoaddeli et al (2003) Physical health; psychological health, social relationships, environment 8 (WHO/QOL26) Negative affectivity (NA) (Affect balance scale) Main effects of personality NA was a significant predictor of MDD-orGAD in women: RR=1.55 (1.33–1.81) and men: RR= 1.98 (1.66–2.36) it partially accounted for the effect of high job demands. In men, the effect of high job demand RR =2.00 (1.13–3.56) reduced to RR= 1.84 (1.09–3.11) with NA controlled. In women, the corresponding RR values were: RR= 1.90 (1.22–2.98) reduced to RR= 1.79 (1.16–2.76) SOC was significant for each health outcome: Physical health (β = .21**) Psychological health (β = .12***) Social relationships (β = .13***) NA predicted selfrated physical health (β= -.05*) Tests of personality x psychosocial work factors interactions reported ? Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects No ___ No ___ 29 Author Niedhammer et al (2004) Sample Follow-up duration Dependent measure (s) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Personality measures Ota et al (2009) 11 Tests of personality x psychosocial work factors interactions reported ? Self-reported health (SRH) Analysis restricted to those who reported ‘good’ SRH at baseline ERI measures of effort and reward Overcommitment (OC) Demographics Occupation Stressful events Chronic conditions Depression Lifestyle factors High OC was a significant predictor of poor SRH among men, OR=1.67 (1.322.12), but not among women. ERI was not significant when controlled for OC No Employees aged 19-56 yrs (Swedish Level of Living survey) T1 response rate 76.3% Panel analysis, N=2246 9 yrs ‘Excellent’ health contrasted with: psychological distress; musculoskeletal pain; poor self-rated health (all derived from a single measure) Longitudinal analysis was restricted to those with adverse work conditions at baseline Job demand Job control Physical/ ergonomic work demands Abbreviated SOC measure 3 items Age, health status, gender, marital status, and work hours at baseline Not reported (SOC was only considered to be a potential moderator) Yes 730 middleaged Japanese workers 2 yrs Onset of insomnia (defined with reference to (DSM-IV) Analysis excluded those with insomnia at baseline ERI measures of effort and reward Overcommitment (OC) Sex, age, illness, occupational conditions (manager, shiftwork, overtime) drinking and smoking status at baseline High OC (upper tertile) was significant risk factor for onset of insomnia: No 9 10 Main effects of personality 1 yr GAZEL cohort (France) 4475 men 1811 women Olsson et al 2009 Confounding /control variables included in analysis model DCS model OR=1.75 (1.16-2.66)*** Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects ____ ☺ When exposed to high strain conditions, high (relative to low) SOC increased the probability of ‘excellent’ health (OR = 2.35**), and reduced the probability of musculo-skeletal problems (OR=.34**) ___ 30 Author Paterniti et al (2002) Sample GAZEL cohort (France) Analysis sample N = 10159 Follow-up duration 3 yr Dependent measure (s) Depression (CES-D selfreport scale, 20-item) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Analysis of change in CES-D scores over 3 yr follow-up, adjusted for baseline level Decision latitude Job demand Social support (16-item scale) Personality measures Hostility Self-esteem Type A (Bortner scale) Confounding /control variables included in analysis model Main effects of personality Demographics Stressful personal events Chronic diseases Physical workload Lifestyle factors Risk factors for increased depression: Self-esteem (low) B= -0.13 (0.01)*** M B= -0.17 (-0.03)*** F Hostility (high) B = 0.07 (0.01)*** M B = 0.11 (0.02)***F (Type A, ns) Manual workers N=343 Professionals N=658 3 waves of data collection over 15 months Mental strain (GHQ-12 measure) Control for baseline mental strain 14 1365 White collar employees in a Japanese company ERI model Effort / reward components ER imbalance 1 yr 5 samples in successive years. Response rates 5068% Onset of major depression (Zung Self-rating Depression Scale, and DSM-IV diagnostic criteria) First onset cases compared with never-ill cases Perceived job stress 3 specific workrelated events Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects ☺ Exploratory tests of multiple interactions: Among men, two interactions were found: Decision latitude x hostility (B= -0.009** (s.e.= 0.003) Social support x selfesteem (B= -0.01** (s.e.= 0.004) No interactions reported for women Overcommitment (OC) None OC contributed significantly to mental strain among professionals (β = .14*), but not among manual workers, over and above ERI and DCS measures No ____ Neuroticism, extraversion, openness (from the Five-Factor NEO Inventory) Non-significant factors dropped from final model Neuroticism was a significant risk factor, OR=3.59 (2.06-6.26) Final model also included significant effects of work events OR =1.50 (1.18–1.90) and lack of social support OR= 2.55 (1.58–4.10) No _____ DCS model Demand Control Support 13 Tokuyama et al (2003) Yes Personality and psychosocial stressors were independent predictors of change in depression. 12 Rydstedt et al 2007 Tests of personality x psychosocial work factors interactions reported ? 31 Author Wickrama, et al (2008) Sample 318 U.S. men (from Iowa Mid-life Transition study) employed throughout the followup years Follow-up duration 10yrs 4 waves of data collection (1991, 1992, 1994, 2001) Dependent measure (s) Depressive symptoms from SCL-90-R scale Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Baseline data included in analysis model Work control Personality measures Personal control (LOC) Tests of personality x psychosocial work factors interactions reported ? Significant interactions between personality x work factors ☺☺ indicates initial Confounding /control variables included in analysis model Main effects of personality Education Latent growth curve modeling Higher levels of work control (1991) and increase in work control (1991-94) were negatively related to poor health and depressive symptoms (2001). These effects were fully mediated by level of personal control (1991) and change in personal control (1991-94) No _____ Structural model: T2 NA and T2 workload predicted T2 emotional exhaustion, after control for T1 NA and T1 workload Yes ☺☺ LISREL sub-group analyses (Pearlin,1981, Mastery scale) Poor self-rated physical health (mean of 2 items) 15 hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects JOB-RELATED AFFECTIVE WELL-BEING Houkes et al (2003) 16 338 Bank employees /teachers, mean age 44 yrs. 55% response rate at baseline, 30% for two-wave panel data 1 yr Emotional exhaustion (Dutch version of MBI) Work motivation Turnover intention Yes Task characteristics NA (from Dutch version of PANAS) Workload Social support Upward striving (US) Growth need strength (GNS) Gender Age NA x Workload predicted emotional exhaustion in both synchronous and crosslagged T1/T2 analysis NA x social support interaction was ns. US and GNS measures did not show moderating effects 32 Author Jimmieson et al (2004) Sample Follow-up duration 213 Government employees (Australia) 2 yrs 457 Finnish employees from a random sample of the working age population 45% response rate at T1 1 yr 409 Finnish health care personnel 46% response at baseline 2 yrs Dependent measure (s) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Psychological well-being and client engagement (MBI) Job satisfaction (4 items) Yes Workload Job satisfaction Emotional exhaustion (MBI) Mental distress (GHQ-12) Physical symptoms (10 items) Yes Work engagement (absorption, vigor, dedication) Yes Role ambiguity during work relocation/reorganization Personality measures Tests of personality x psychosocial work factors interactions reported ? Confounding /control variables included in analysis model Main effects of personality Self-efficacy (related to the organizational change process) No T1 Self efficacy predicted T2 client engagement Yes Optimism (Life Orientation Test) Age Education Leadership position Self-esteem and optimism were both significant negative predictors of mental distress (β= -.21**) and emotional exhaustion (β= -.19**) among men, but not among women Yes Self-esteem did not predict any of the outcome scales after control for baseline levels. In the fully adjusted model, job insecurity (negatively) and job control (positively) predicted dedication. No Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects ☺☺ Self-efficacy moderated the effects of T1 role ambiguity (β = .14, p < .05) and T1 workload (β= .16, p < .01 on T2 job satisfaction 17 Makikangas & Kinnunen (2003) 18 Mauno et al (2007) 19 Time pressure Lack of control Job insecurity Poor organizational climate Workload Job insecurity Work-family conflict Job control Management quality Self-esteem (Rosenberg scale) Self-esteem related to the organization Demographics Structural work variables ☺ 3/16 two way interactions work stressor x self-esteem were significant for men, 0/16 for women 3/16 two-way interactions work stressor x optimism were significant for women. 0/16 for men ___ 33 Author Michielsen at al (2004) Sample Follow-up duration 325 participants randomly chosen by phone contact, working at least 20 hrs per week 2 yrs 542 1 yr Dependent measure (s) Emotional exhaustion (MBI) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Yes Workload Personality measures Main effects of personality Gender, age children Employment contract (permanent/ temporary) Marital status Number of work hours/week Reduced structural model Hardiness (β = - 0.10*) predicted T2 emotional exhaustion, but not T2 fatigue after control for T1 levels. Other personality variables were ns in initial model and were dropped from the analysis No Locus of control (LOC) (measure based on Spector Work Locus of Control scale) Age Gender Main effect of LOC was non-significant. Yes Self-efficacy (Latent variable with two indicators) Age Type A (JAS) Hardiness FFPI measures Extraversion General fatigue Agreeableness Conscientious -ness Emotional stability (NA) Autonomy 20 Rodriguez et al (2001) European data processing operators 171 men 371 women 21 Age 18-36 yrs, mean 22.6 yrs, at baseline Schwarzer et al (2008) 458 German teachers 22 2nd and 3rd waves of a 3-wave, 3yr study 1 yr Job dissatisfaction (assessed by standardized interview) Yes Burnout (MBI) Yes Job demands Job control Social support (non-standard DCS measures) Job stress (15-item scale) Tests of personality x psychosocial work factors interactions reported ? Confounding /control variables included in analysis model Significant main effects of support and demands. Structural modeling analyses: T1 self efficacy predicted T2 burnout; no evidence of reverse causation. Relationship between self-efficacy and burnout was fully mediated by work stress No Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects ___ ☺☺ Significant demand x control x social support x locus of control interaction. Job demand x control interaction was significant only for internal LOC participants under conditions of high support. ____ 34 Author Tyssen et al (2005) Sample 371 hospital medical interns Follow-up duration 1 yr Dependent measure (s) Perceived job stress Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Perceived stress at medical school Work hours Sleep hours Organizational climate Personality measures Neuroticism Extraversion Compulsiveness/control Confounding /control variables included in analysis model Age Gender 23 Feldt et al (2000) 25 In adjusted model: NA was significant, B = 1.7*** (.94-2.95) Other personality variables, all ns. Sleep hours and organizational climate were significant. Tests of personality x psychosocial work factors interactions reported ? Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects No (interactions with gender were tested) (NA interacted significantly with gender) 219 Finnish employees in health care and service organization 159 women 60 men 1 yr 2-wave panel study Emotional exhaustion (MBI) Psychosomatic symptoms Yes Job insecurity Influence at work Leadership relations Organizational climate Sense of coherence SOC Age Education Gender Structural equation modeling (LISREL) SOC mediated the relationship between level of job insecurity and levels of psychosomatic symptoms and emotional exhaustion. Intra-individual change in SOC mediated the effects of changes in organizational climate and leadership relations on both outcomes No _____ 615 Finnish employees, (trades union members) 94% men Response rates 64% (T1) 70% (T2) 3 yrs 2 wave panel study Anxiety Comfort Depression Enthusiasm (4 factors from Warr scale of job-related affective wellbeing Yes Job control Supportive organizational climate Sense of coherence SOC Gender Age Managerial level Structural equation modeling (LISREL) Direct and reverse causal models were tested. T2 outcomes were not predicted by SOC, but weak evidence of one reverse causal path was found (T1 ‘comfort’ factor to T2 organizational climate). Curvilinear paths between work measures and affective outcomes were ns. No ____ 24 Makikangas et al (2007) Main effects of personality 35 Author Sample Follow-up duration Dependent measure (s) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Personality measures Confounding /control variables included in analysis model Main effects of personality Tests of personality x psychosocial work factors interactions reported ? Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects JOB-RELATED BEHAVIOURAL OUTCOMES Cavanaugh et al (2000) 26 Elovainio et al (2003) ‘High-level’ managers (U.S.) 91% were male. Analysis sample N=671 (19% response 1 yr Voluntary turnover n/a Job stress measures: Challenge stress (6 items) Hindrance stress (5 items) NEO fivefactor model Neuroticism, Extraversion Conscientious -ness Gender 2 yr Sickness absence (Formal records of self-certified sickness) Yes Measures of relational and procedural organizational justice Hostility Neuroticism Age Salary Baseline sickness absence 28 Poisson regression model. Hostility had main effects on absence for men (β= .15***) and for women (β=.03**). Yes 260 working adults in two companies Mean age 36.9 yrs Response rate 60% 1 yr Health care usage assessed by records of costs and claims Yes Stressful work events Social support Hardiness Type A behaviour ____ Gender Age Ethnicity Education Exercise Quality of life Personality measures and psychosocial variables were ns. Only ‘stressful work events’ predicted health care costs ☺☺ Two interactions were significant for men, but not women: Relational justice x neuroticism (β= -.08**) Neuroticism had main effects on absence for men (β= .08*) and women (β= .05***) 27 Fusilier & Manning (2005) No Extraversion (β=.04*) Hindrance-related job stress (β=.74**) Neuroticism and conscientiousness (ns) at T1, and 45% response from T1 respondents at T2) Hospital employees 506 men 3570 women In maximum likelihood model predicting voluntary turnover: Procedural justice x hostility (β= -.08*) No ___ 36 Author Ostry et al (2004) Sample 1886 Canadian sawmill workers 62.8% response Follow-up duration 1 yr Dependent measure (s) Physician visits for mental health reasons, or 30+ visits for any reason (from ‘Linked Health Data Base’) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Participants with mental health visit in previous year, or hospitalized in previous year were excluded Job strain model Job control Job demand Personality measures Overcommitment (OC) Confounding /control variables included in analysis model Main effects of personality Sociodemographic variables No significant effects of OC Job strain and ERI were ns in relation to physician visits for mental health reasons. Nonpsychosocial work conditions variables ERI model Effort / reward components ER imbalance 30 No Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects ____ Low ER status control 1.32* (1.01 – 1.82), and Low ER esteem reward, 1.63** (1.19 – 2.23) were risk factors for 30+ physician visits 29 Vahtera et al (2000) Tests of personality x psychosocial work factors interactions reported ? 757 municipal employees (response rate, 77%) Mean age 41 yrs 6 yrs (3 yrs during downsizing, and 3 yrs following downsizing) Sickness absence rates derived from municipal records Control for baseline health status Down-sizing Job control (18 item scale) Hostility High versus low Age Gender Income Significant overall effects of hostility during and after down-sizing. Rate ratios relative to low hostility reference group: High hostility during: 1.21 (1.06–1.39) High hostility after: 1.38 (1.22–1.55) Yes ☺ Significant interaction (p<.05) between job control (good vs poor) and hostility (high vs low) in predicting sick leave rates only during down-sizing. After down-sizing, the job control x hostility interaction was nonsignificant 37 Author Sample Follow-up duration Dependent measure (s) Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Personality measures Confounding /control variables included in analysis model Main effects of personality Tests of personality x psychosocial work factors interactions reported ? Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects CORONARY HEART DISEASE OUTCOMES Kuper, SinghManoux, et al (2002) Whitehall II 6895 male and 3413 female civil servants at baseline 11 yrs (mean) Phase 1 baseline to Phase 5 Validated incident coronary heart disease events. Incident cases ERI model (proxy scales derived from other measures) Effort, reward ERI OC (single item proxy measure, 5point scale dichotomized for analysis) Age Gender Coronary risk factors High OC was a risk factor for incident CHD at follow-up in adjusted model. OR= 1.26(1.09 –1.46) Highest quartile ERI relative to lowest quartile: OR=1.26 (1.03–1.55) Yes Whitehall II 10308 UK civil servants 12.5 yrs (mean) Phase 1 (baseline) to Phase 7 Fatal CHD (from NHS records) Non-fatal myocardial infarction, angina (self-report, clinically verified) Incident cases DCS model Job demand Job control Social support NA PA Affect balance Age Gender Ethnicity Employment grade Smoking, Alcohol, and other health behaviors/lifestyle factors Hypertension Highest tertile of NA was a significant risk factor for incident coronary heart disease, HR = 1.32 No ☺ No evidence of significant ERI x OC interaction. For High ERI quartile in adjusted model: High OC: OR=1.39 (1.05–1.85) Low OC: OR=1.31 (0.98–1.75) 31 Nabi et al (2008) 6895 men 3413 women Cholesterol 32 (1.09 to 1.60), in model adjusted for demographic factors. Control for job strain, and other potential confounders did not substantially change this finding. No significant effects of PA or affect balance _____ 38 Author Nabi, SinghManoux, et al (2008) Sample Whitehall II 6396 civil servants 4453 men 1943 women Follow-up duration 11.1yrs (mean) Phases 1-2 baseline, follow-up Phases 3-7 Dependent measure (s) Coronary heart disease (CHD) Fatal CHD from NHS records; non-fatal myocardial infarction and angina was determined from medical records Control for initial/ baseline level of dependent measure(s) Exposure measure(s) Free of clinically validated CHD at start of follow-up period DCS model Job demands Decision latitude Social support at work Personality measures NA (average of Phase I and Phase 2 assessments) Confounding /control variables included in analysis model Main effects of personality Age Gender Ethnicity Employment grade Smoking Alcohol, and other health behaviors/lifestyle factors Hypertension NA was a risk factor for CHD incidence, adjusted for all confounders including psychosocial stress (iso-strain) at work: Cholesterol 33 RII=1.64(1.17-2.32)** Control for inflammatory markers did not attenuate this risk; therefore, inflammatory markers did not mediate the direct NA→ CHD link * p<.05 ** p<.01 ***p<.001 SOC Sense of coherence LOC Locus of control NA Negative affectivity/neuroticism PA Positive affectivity MBI Maslach Burnout Inventory GHQ General Health Questionnaire SRH Self-reported health OC Over-commitment DCS Demand-Control-Support model ERI Effort-Reward Imbalance model CHD Coronary heart disease NHS National Health Service (UK) Tests of personality x psychosocial work factors interactions reported ? No Significant interactions between personality x work factors ☺☺ indicates initial hypotheses predicted specific personality x work moderating effects ☺ Exploratory analyses of moderating effects _____ 39 References list for studies included in Table 2.2 1. Bridger, R.S., Brasher, K., Dew, A. & Kilminster, S. (2008). Occupational stress and strain in the Royal Navy 2007. Occupational Medicine, 58, 534-539. 2. Buddeberg-Fischer, B., Klaghofer, R., Stamm, M., et al. (2008). Work stress and reduced health in young physicians: Prospective evidence from Swiss residents. International Archives of Occupational and Environmental Health, 82, 31-38. 3. Burgard, S.A., Brand, J.E. & House, J.S. (2009). Perceived job insecurity and worker health in the United States. Social Science and Medicine, 69, 777-785. 4. Godin, I., Kittel, F., Coppieters, Y. & Siegrist, J. (2005). A prospective study of cumulative job stress in relation to mental health. BMC Public Health, 5. http://www.biomedcentral.com.ezproxy.library.uwa.edu.au/content/pdf/1471-2458-5-67.pdf 5. Kivimäki, M., Elovainio, M., Kokko, K., et al. (2003). Hostility, unemployment and health status: Testing three theoretical models. Social Science and Medicine, 56, 2139-2152. 6. Marchand, A., Demers, A. & Durand, P. (2005). Do occupation and work conditions really matter? A longitudinal analysis of psychological distress experiences among Canadian workers. Sociology of Health and Illness, 27, 602-627. 7. Melchior, M., Caspi, A., Milne, B.J., et al. (2007). Work stress precipitates depression and anxiety in young, working women and men. Psychological Medicine, 37, 1119-1129. 8. Nasermoaddeli, A., Sekine, M., Hamanishi, S. & Kagamimori, S. (2003). Associations between sense of coherence and psychological work characteristics with changes in quality of life in Japanese civil servants: A 1-year follow-up study. Industrial Health, 41, 236-241. 9. Niedhammer, I., Tek, M.L., Starke, D. & Siegrist, J. (2004). Effort-reward imbalance model and self-reported health: Cross-sectional and prospective findings from the GAZEL cohort. Social Science and Medicine, 58, 1531-1541. 10. Olsson, G., Hemström, O. & Fritzell, J. (2009). Identifying Factors Associated with Good Health and Ill Health - Not Just Opposite Sides of the Same Coin. International Journal of Behavioral Medicine, 1-8. 11. Ota, A., Masue, T., Yasuda, N., et al. (2009). Psychosocial job characteristics and insomnia: A prospective cohort study using the Demand-Control-Support (DCS) and Effort-Reward Imbalance (ERI) job stress models. Sleep Medicine, 10, 1112-1117. 12. Paterniti, S., Niedhammer, I., Lang, T. & Consoli, S.M. (2002). Psychosocial factors at work, personality traits and depressive symptoms: Longitudinal results from the GAZEL Study. British Journal of Psychiatry, 181, 111-117. 13. Rydstedt, L.W., Devereux, J. & Sverke, M. (2007). Comparing and combining the demand-control-support model and the effort reward imbalance model to predict long-term mental strain. European Journal of Work and Organizational Psychology, 16, 261-278. 14. Tokuyama, M., Nakao, K., Seto, M., et al. (2003). Predictors of first-onset major depressive episodes among white-collar workers. Psychiatry and Clinical Neurosciences, 57, 523-531. 15. Wickrama, K.A.S., Surjadi, F.F., Lorenz, F.O. & Elder Jr, G.H. (2008). The influence of work control trajectories on men's mental and physical health during the middle years: Mediational role of personal control. Journals of Gerontology - Series B Psychological Sciences and Social Sciences, 63, S135-S145. 16. Houkes, I., Janssen, P.P.M., De Jonge, J. & Bakker, A.B. (2003). Personality, work characteristics, and employee well-being: A longitudinal analysis of additive and moderating effects. Journal of Occupational Health Psychology, 8, 20-38. 40 17. Jimmieson, N.L., Terry, D.J. & Callan, V.J. (2004). A Longitudinal Study of Employee Adaptation to Organizational Change: The Role of Change-Related Information and Change-Related Self-Efficacy. Journal of Occupational Health Psychology, 9, 11-27. 18. Mäkikangas, A. & Kinnunen, U. (2003). Psychosocial work stressors and well-being: Self-esteem and optimism as moderators in a one-year longitudinal sample. Personality and Individual Differences, 35, 537557. 19. Mauno, S., Kinnunen, U. & Ruokolainen, M. (2007). Job demands and resources as antecedents of work engagement: A longitudinal study. Journal of Vocational Behavior, 70, 149-171. 20. Michielsen, H.J., Willemsen, T.M., Croon, M.A., et al. (2004). Determinants of general fatigue and emotional exhaustion: A prospective study. Psychology and Health, 19, 223-235. 21. Rodriguez, I., Bravo, M.J., Peiro, J.M. & Schaufeli, W. (2001). The Demands-Control-Support model, locus of control and job dissatisfaction: A longitudinal study. Work and Stress, 15, 97-114. 22. Schwarzer, R. & Hallum, S. (2008). Perceived teacher self-efficacy as a predictor of job stress and burnout: Mediation analyses. Applied Psychology, 57, 152-171. 23. Tyssen, R., Vaglum, P., Grønvold, N.T. & Ekeberg, Ã. (2005). The relative importance of individual and organizational factors for the prevention of job stress during internship: A nationwide and prospective study. Medical Teacher, 27, 726-731. 24. Feldt, T., Kinnunen, U. & Mauno, S. (2000). A mediational model of sense of coherence in the work context: A one-year follow-up study. Journal of Organizational Behavior, 21, 461-476. 25. Mäkikangas, A., Feldt, T. & Kinnunen, U. (2007). Warr's scale of job-related affective well-being: A longitudinal examination of its structure and relationships with work characteristics. Work and Stress, 21, 197219. 26. Cavanaugh, M.A., Boswell, W.R., Roehling, M.V. & Boudreau, J.W. (2000). An empirical examination of self-reported work stress among U.S. managers. Journal of Applied Psychology, 85, 65-74. 27. Elovainio, M., Kivimäki, M., Vahtera, J., et al. (2003). Personality as a moderator in the relations between perceptions of organizational justice and sickness absence. Journal of Vocational Behavior, 63, 379-395. 28. Fusilier, M. & Manning, M.R. (2005). Psychosocial predictors of health status revisited. Journal of Behavioral Medicine, 28, 347-358. 29. Ostry, A.S., Hershler, R., Chen, L. & Hertzman, C. (2004). A longitudinal study comparing the effort-reward imbalance and demand-control models using objective measures of physician utilization. Scandinavian Journal of Public Health, 32, 456-463. 30. Vahtera, J., Kivimäki, M., Uutela, A. & Pentti, J. (2000). Hostility and ill health: Role of psychosocial resources in two contexts of working life. Journal of Psychosomatic Research, 48, 89-98. 31. Kuper, H., Singh-Manoux, A., Siegrist, J. & Marmot, M. (2002). When reciprocity fails: Effort-reward imbalance in relation to coronary heart disease and health functioning within the Whitehall II study. Occupational and Environmental Medicine, 59, 777-784. 32. Nabi, H., Kivimäki, M., De Vogli, R., et al. (2008). Positive and negative affect and risk of coronary heart disease: Whitehall II prospective cohort study. BMJ, 337, 32-36. 33. Nabi, H., Singh-Manoux, A., Shipley, M., et al. (2008). Do psychological factors affect inflammation and incident coronary heart disease: The Whitehall II study. Arteriosclerosis, Thrombosis, and Vascular Biology, 28, 1398-1406. 41 3. Personality change over the life course Personality traits are considered to be ‘relatively enduring’ patterns of thoughts, feelings and behaviours that distinguish individuals from one another. However, this definition does not imply that personality traits do not change over the adult life span, although the time course and extent of change has been disputed. Thus, some researchers argue for a ‘plaster’ theory, claiming that there is little change in personality beyond the age of about 30 years106,107; others, endorsing a ‘plasticity’ theory, consider that personality traits continue to change in middle and old age108,109. The two main approaches to studying personality change and continuity over the life course are evaluation of mean-level change and evaluation of individual differences in patterns of change. Mean-level change refers to increases or decreases in specific personality traits over a specified period in the life course for a population of individuals; individual differences in patterns of change reflect deviations from these normative meanlevel trends110. Individual differences in the nature and extent of personality change over time affect the relative rank-order placement of individuals within the group, designated consistency. Thus, rank-order consistency can be maintained even when mean-level changes occur; similarly, rank-order can change without necessarily bringing about a change in mean level. In the following sections, patterns of mean-level personality change are described, and individual differences in personality change across the life course, and the factors b associated with such changes, are then examined . 3.1 Mean-level changes in personality across the life course Mean-level change in personality is usually regarded as representing normative change, which occurs when most people change in the same way during a specific period within the life course. The term maturity principle has been used to describe this normative pattern of increasing psychological maturity from adolescence to middle age111. Although normative, mean-level personality changes occur predominantly in young adulthood (2040 years), some change may continue throughout the life course. 3.1.1 Mean-level change in personality traits assessed by the Five Factor Inventory The Five Factor Inventory (e.g. NEO-FFI)87, which assesses the personality characteristics of extraversion, neuroticism, conscientiousness, openness, and agreeableness, has been extensively used to study mean-level patterns of personality change across the lifespan in both cross-sectional and longitudinal samples112-114, 115. A meta-analysis of 92 longitudinal studies covering the age range from 10 to 101 yrs demonstrated a clear pattern of normative change in NEO-FFI personality traits across the life course109,110. b The papers cited in this section were located by a search of computer databases, focusing primarily on literature published in the past 10 years. 42 In general, with increasing age, people became more conscientious and emotionally stable. The most marked changes occurred in young adulthood, but different facets of personality showed different profiles across age groups and some changes continued into middle and old age. Thus, conscientiousness and agreeableness tended to increase steadily throughout the life course, while emotional stability increased relatively little beyond the age of 40 years, and openness to experience decreased in the 50+ age groups. Extraversion showed more complicated patterns; one component, social dominance, increased with age, while a second component, social vitality, showed small increases in adolescence and small decreases late in life110. A recent study of students in transition from school to college over a two-year period also found mean-level changes consistent with the maturity principle; scores on agreeableness, conscientiousness, and openness increased over time, whereas neuroticism decreased116. A separate study found that the rank-order consistencies of the major dimensions and most trait facets of the NEO-FFI were unrelated to age, although some scales showed increasing stability after age 30 years107. Whilst poorer psychometric properties of personality inventories in young people might account for the apparent lesser stability of traits in younger groups, evidence from a psychometric evaluation showed that measurement unreliability did not explain the findings; rather, the underlying traits were found to be less stable in young adults117. In two further studies, confirmatory factor modelling methods were used to analyse crosssectional and longitudinal datasets from a Dutch sample of middle-aged and older adults118,119. This study used the FFPI inventory 120 which assesses traits similar to those covered by the NEO-FFI, except that a measure of autonomy replaces the NEO-FFI openness measure. The results showed a particularly marked increase in conscientiousness across the age range of 16-70+ years, smaller increases in agreeableness and emotional stability, a decrease in extraversion and, from age 60 yrs, an abrupt decrease in autonomy. In general, men and women show similar profiles of mean-level change although some evidence suggests that increases in emotional stability with age are greater among women than among men. Thus, in a large cross-sectional study of U.S. and Canadian individuals (N=132,515, age range 21-60 yrs), recruited through the Internet, emotional stability continued to increase across the age span among women whereas there was little change in scores either below or above the age of 30 years among men108. 3.1.2 Mean-level change in ‘sense of control’ The NEO-FFI personality inventory, on which most of the findings related to mean-level change over time are based, does not include a measure of locus of control. However, ‘sense of control’ refers to a similar personality characteristic (i.e. the extent to which individuals regard themselves as responsible for their own successes and failures rather than believing that outcomes are due to luck or chance, and unrelated to ability or effort), and stability and change in this measure has been examined in several studies. 43 Two large national surveys of adults showed that mean levels of sense of control remained stable and relatively high in the age range 18-50 years, followed by progressive decreases in older age groups121. The pattern of age-related change was not markedly altered by controlling for potential confounders122; this analysis also showed that the generally lower sense of control among women as compared with men was more marked in older age groups. Over time, women's sense of control declined more sharply than that of men. Differences in education, personal employment history, household income, and physical functioning accounted for some of the age-related effects of gender. The role of education in promoting a sense of control is particularly important; among those with higher levels of education, sense of control tends to increase for longer, rise higher, and decrease more slowly with age123. Factors found to underlie the link between education and sense of control include more challenging and interesting work, greater control over schedules, and greater economic rewards and security, which are associated with higher status occupations124. Among older, chronically ill adults, sense of control was found to decline gradually over six successive bimonthly assessments; aside from age at baseline, the only other major predictor was mental health125. 3.1.3 Mean level change in ‘Sense of Coherence’ Several studies have examined changes over time in the personality dimension of ‘sense of coherence’(SOC)126. SOC describes a generalised tendency to view the world and the individual environment as comprehensible, manageable, and meaningful; it is conceptualised as a measure of ‘salutogenic’ personal resources, which have a positive influence on health. Antonovsky42 regarded SOC as a ‘dispositional orientation’ rather than a personality trait; he considered that an individual’s SOC should be fully developed by the age of 30 yrs and that, although change might occur subsequently, the stable level would return after the cause of the change had dissipated. The stability or otherwise of SOC measures, and the extent of change with age, has been much debated in the light of mixed findings. In one study, for instance, SOC was not found to be more stable in an older group compared with the younger group; age did not play any role in the stability of, level of, or mean changes in sense of coherence127. In contrast, a systematic review concluded that SOC does tend to increase with age128. Further, and more consistent evidence, demonstrates that SOC is more stable over time among those with high SOC levels as compared with those with low SOC levels129,130. An intervention designed to boost re-employment among unemployed individuals131 provided evidence SOC can change over relatively short time periods. The intervention significantly increased SOC scores, and participants who found employment showed the largest changes. Of the SOC subscales, comprehensibility and manageability showed significant overall increases, while meaningfulness increased only among those who gained employment. However, younger participants (< 30 yrs) did not show more benefit than those who were older. 44 3.2 Individual differences in patterns of personality change Life experiences, particularly in work and relationship roles, contribute to individual patterns of personality change which deviate from normative mean-level changes in personality across the life course111,132,133, possibly even running counter to these normal trends134. Findings from several longitudinal studies demonstrate that work conditions, and occupational factors more generally, contribute to individual personality change over extended periods of time. 3.2.1 Individual personality change: The roles of work and occupational factors Work stress. Evidence suggests that perceived work stress is associated with adverse changes in personality. In a 3-year longitudinal study of personality in relation to midlife parental concerns135, personality was assessed at the first (T1) and third (T3) waves of data collection while aspects of midlife functioning, including work stress and life satisfaction, were assessed at the second wave (T2). Analyses predicting T3 personality measures, controlled for T1, showed that measures of midlife functioning explained significant variance (albeit, only 1 - 4%) in personality change. In particular, among men, work stress was associated with decreases in emotional stability, extraversion and, marginally, agreeableness. In relation to emotional stability, the negative effect of work stress (β = -.20***) was more marked than the positive effect of life satisfaction (β =.12**). However, among women, increases in conscientiousness, openness and agreeableness were positively associated with life satisfaction; work stress was not a significant factor for women. Job loss. As part of a study of heart disease, a large sample of men and women in their 40’s completed the NEO-PI (a version of the Five Factor inventory) at baseline and again 6-9 years later. At follow-up, they also responded to items asking whether they had experienced changes in family, work, health and economic circumstances since baseline. As compared with those who were promoted, those who were fired showed significant decreases in emotional stability and conscientiousness over the follow-up years106. De-investment in work. In a study carried out over 8 years with young adults, deinvestment in work (i.e. engaging in counter-productive behaviours, such as fighting with co-workers, malingering, breaking safety rules) was associated with personality changes between the ages of 18 and 26 years that ran counter to normative trends, i.e. with increase in negative emotionality (e.g. aggression and alienation), and with no increase in traits reflecting constraint and self-control134. Work control. A recent longitudinal study showed that work conditions (specifically, work control assessed by the Karasek measure1) contributed to individual differences in personal control (assessed by the ‘Mastery’ scale 82), and that personal control was related to health measures. In this study, based on data from middle-aged men in a rural U.S. state, Wickrama et al.85 used latent growth curve analysis to test a theoretical model that included both initial level (1991) and rate of change (from 1991 to 1994) in work control and personal control as predictors of physical health and depressive symptoms in 2001 (controlled for 1991 level). 45 Over the three-year period, 1991-1994, a small overall increase in work control was found but there was significant variability across individuals. Over the same period, there was a decreasing trend in personal control but inter-individual variability was relatively small. Significant positive paths were found from level of work control to level of personal control, and from change in work control to change in personal control; moreover, initial level of personal control, and change in personal control, fully mediated the relationships between level and change in work control and health outcomes. Thus, these findings demonstrate that work experiences and changes in work conditions contribute to changes in personal control, which in turn have implications for health change over an extended period. The findings are also consistent with the emphasis placed on the job control dimension in the demand-control model1, although this study extends the model by demonstrating the meditational role of personal control in the relationship between work control and health. Work role quality. Changes in neuroticism and in extraversion were examined in relation to work satisfaction and relationship satisfaction in a five-wave, 8-year longitudinal study136. Latent growth curve modelling was used to test whether neuroticism decreased as work became more satisfying, and whether the relationship varied by age group. The results showed that, as work satisfaction increased, neuroticism decreased, but the relationship did not change across age groups. Similarly, as work satisfaction increased over time, so did extraversion; again, age was not a significant factor. An earlier study carried out over a 30-year period, found similar results; positive role-quality was associated with increases in measures of effective functioning and well-being and decreases in measures of anxiety and neuroticism137. 3.2.2 Reciprocal relations between personality change and work exposures In summary, the studies outlined above show that adverse occupational experiences are associated with negative personality changes. In particular, traits associated with neuroticism increase and conscientiousness decreases; conversely, favourable work experiences are associated with positive personality changes. However, in spite of the longitudinal nature of these studies, researchers are cautious about making causal inferences, noting for instance that “we can conclude only that change in personality is associated with work experiences”133. Underlying this caution is evidence that personality plays a role in determining the work situations that individuals select; people actively seek out environments that fit with their personality133,138. Thus, as has been demonstrated in several studies, relationships between organizational experiences and personality are reciprocal, rather than uni-directional. For instance, among young adults entering employment, personality at age 18 yrs predicted objective and subjective work experiences at age 26 yrs139. Conversely, work experiences were related to changes in personality between 18 and 26 yrs; the traits that selected people into specific work experiences were the same traits that changed in response to these experiences. Higher status, more satisfying jobs, and gaining financial security, were associated with decreases in negative emotionality and increases in 46 sociability, positive dispositional characteristics, and self-esteem. In contrast, those who scored high on negative emotionality at age 18 years experienced difficult transitions into employment; by age 26 years they occupied lower prestige jobs, were less satisfied with their jobs, and reported financial difficulties. More recent findings also illustrate reciprocal transactions between work experiences and personality140. In this study, personality characteristics, and extrinsic (income and occupational prestige) and intrinsic (job satisfaction) measures of career success, were assessed at the start and end of a 10-yr interval. Cross-lagged analyses tested whether personality predicted change in career success over the 10-year interval and, likewise, whether markers of career success predicted change in personality. The main findings were that, among younger participants, baseline income predicted decreases in neuroticism over the follow-up period, and baseline extraversion predicted increases in income, but these findings did not hold for older participants, nor did they apply to the other occupational measures. Whilst not directly concerned with work conditions, there is also evidence of reciprocal relationships over a 2-3 yr period between life stressors and personality, specifically neuroticism and anxious depression141. Although Wickrama et al 85 examined only uni-directional paths between work control, personal control and health, evidence from previous studies indicates that there are reciprocal relationships between locus of control and work experiences. Thus, in a sample of middle-aged males, analysis of survey data spanning a two-year interval, demonstrated that locus of control systematically influenced work success and, conversely, success at work enhanced internal locus of control97. Similar findings were reported for school leavers entering private-sector employment, but in public-sector employment the opposite was true, career progress leading to increased externality, although this effect was of only marginal significance142. A more extensive study98, in which baseline and 10-yr follow-up data were analysed using structural equation modelling, also demonstrated reciprocal relations between personality and job conditions. In particular, ‘self-directed orientation’ (a dimension similar to locus of control), ideational flexibility (a measure of problem-solving ability), and occupational self-direction (substantively complex work) were found to act as a ‘mutually reinforcing triumvirate’, each influencing the others over time. 3.3 Implications Findings relating work experiences to individual patterns of personality change over the life course highlight the importance of promoting work conditions that reinforce favorable, health-promoting personality changes. In particular, research demonstrating that adverse work situations (e.g. work stress, job loss, low job control) are associated with increases in neuroticism raises serious concerns in view of evidence that high neuroticism at baseline and an increase in neuroticism over subsequent years are independent predictors of mortality risk143. 47 From a methodological viewpoint, the reciprocal nature of relations between personality traits and work experiences suggests that, in longitudinal studies of work-related psychosocial risk factors and health, salient personality characteristics should be measured on more than one occasion, and appropriate bi-directional paths incorporated into the causal models tested. Latent growth curve models offer a valuable method of analyzing such data. Moreover, there is a need for long-term cohort studies; as Wickrama et al.85 concluded, ‘an investigation of health outcomes in the middle years calls for a “long view” so that health consequences of adverse work conditions in early midlife can be documented later, as they emerge in later midlife’. Moreover, such work calls for collaboration among medical scientists, epidemiologists, and social scientists if research resources are to be used to best effect to increase understanding of the complex patterns of change over time in work conditions, individual characteristics, and health. 48 4. Psychometric issues: Reliability and validity of personality tests The research cited in this report identifies a range of personality attributes implicated in the processes by which work-related psychosocial risks are linked to adverse health outcomes. Interpretation of this research requires an understanding of the psychometric properties of personality measures concerned. This section outlines methods used in the development and evaluation of personality measures, and examines evidence of the psychometric properties of several scales widely used in psychosocial research. 4.1 Scale development In the development of a personality test, a large number of items relevant to the personality attribute of interest are generated for initial data collection purposes; factor analysis methods are then used to analyse the data matrices and determine the underlying factor structure. Initial exploratory factor analyses allow identification of the minimum number of dimensions that account for scores on the test items, and facilitate rejection of ambiguous or unsuitable items that do not fit the hypothesised model. Confirmatory factor analysis methods, applied to data from a new sample, can then be used to evaluate the goodness-of-fit of the factor solution derived from the initial exploratory analysis. Hence, it is possible to create scales to assess separate personality characteristics or to identify sub-scales representing different facets of a single personality attribute. The psychometric properties of these scales can then be evaluated. The stages involved in the development of personality measures, and the problems and pitfalls that may be encountered, have been detailed in a review by Furnham144. In recent years, the development of a new statistical approach, ‘Item Response Theory’ (IRT)145, which models the relationship between latent traits and responses to test items, has brought greater sophistication and flexibility to psychometric methods, leading to improved reliability of assessment. 4.2 Reliability and validity In selecting a test to assess any particular personality attribute, issues of reliability and validity are important considerations. The methods traditionally used to assess reliability and validity in the development and evaluation of personality tests are outlined below. 4.2.1 Reliability Reliability refers to the consistency of a test; a test is reliable to the extent that whatever it measures, it measures it consistently. There are several ways of assessing reliability. The two most important are (i) internal consistency which measures homogeneity, that is, the degree to which the items jointly measure the same construct, and (ii) ‘test-retest’ reliability which measures stability over repeated administrations of the same test. The most frequently reported measure of reliability is ‘coefficient alpha’ (a measure of internal 49 consistency). The minimum acceptable value of alpha is normally considered to be .70146. For research purposes, reliability should generally be greater than .80, while standardized tests used for clinical or educational purposes should have alpha values greater than .90147. The maximum possible value of a correlation between two variables is inherently attenuated by reliability; low reliability also lessens power against Type II (false negative) errors148. Thus, the reporting of effect sizes requires that the reliability of the test scores is known, and that effect sizes are interpreted in the light of the reliability estimates. Moreover, as different samples, test conditions, and other factors can affect observed scores and hence reliability estimates, reliability should be reported for the actual scores obtained in the study, rather than relying on estimates from prior studies or test manuals. 4.2.2 Validity Validity can be defined as the agreement between a test score and what it is intended to measure. Validity can be assessed in several different ways. • Construct validity. There are two aspects of construct validity. Convergent validity refers to whether a test correlates well with other tests that measure the same construct, or with which it should theoretically correlate. Discriminant validity requires that a test has low correlations with tests of unrelated constructs, i.e. it measures something different from other scales designed to measure different conceptual variables. To establish construct validity, both convergent and discriminant validity are necessary. • Concurrent and predictive validity. If a test correlates with a criterion measure which is known to be valid and assessed at the same time point, it is said to have concurrent validity. When information about the criterion measure is collected at a later time point, the aim is to establish predictive validity. These two aspects of validity are the focus of the present review. In addition, two further aspects of validity are concerned with the actual content of the items: • Face validity refers to whether the content of the test items appears to be reasonably related to the perceived purpose of the test. • Content validity refers to the adequacy of the representation of the domain (e.g. extraversion) that the test is designed to cover. It requires ensuring that the items are a fair and representative sample of the potential content, and appropriately worded for the population or group concerned. 4.3 Fairness in psychometric testing In recent years, issues relating to the fairness, appropriateness and validity of tests and test procedures have been subject to increased scrutiny, particularly in the context of education and employment-related testing. These concerns have given rise to formal guidelines, such as the American Psychological Association document149, covering legal, professional, and ethical issues in the construction and application of psychometric tests. 50 5. Psychometric properties of specific personality measures The following sections summarise information about the psychometric properties of several well-established personality measures relevant to studies of work-related psychosocial risks and health. Particular attention is given to personality characteristics that significantly predicted mental and physical health outcomes in the prospective studies reviewed in Section 2. In each case, evidence of test reliability and validity is summarised with reference to literature findings. Examples of the tests described, when available, are shown in the Appendix. c 5.1 The NEO Five-Factor personality measures The NEO Five-Factor Model is currently the most widely accepted model of personality structure; it has generated a vast literature (to date, the manual for the NEO personality measures87 has received more than 4000 citations). The ‘Revised NEO Personality Inventory’ (NEO-PI-R) assesses 30 trait measures that define five basic domains of normal personality, Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness. Each of the NEO-PI-R trait measures has 8-items; each of the five domains has 48 items (240 items in total). The traits that make up the five personality domains are listed below: • • • • • Neuroticism: anxiety (N1), anger–hostility (N2), depression (N3), selfconsciousness (N4), impulsiveness (N5) and vulnerability (N6). Extraversion: warmth (E1), gregariousness (E2), assertiveness (E3), activity (E4), excitement-seeking (E5) and positive emotions (E6). Openness to experience: fantasy (O1), aesthetics (O2), feelings (O3), actions (O4), ideas (O5) and values (O6). Agreeableness: trust (A1), straightforwardness (A2), altruism (A3), compliance (A4), modesty (A5) and tender mindedness (A6). Conscientiousness: competence (C1), order (C2), dutifulness (C3), achievement striving (C4), self-discipline (C5) and deliberation (C6). In addition to the NEO-PI-R and the shorter 60-item ‘NEO Five-Factor Inventory’ (NEOFFI)87,150, a simpler version (NEO-PI-3) has been produced to meet criticisms that the NEO items were not always readily understood151. Other authors have described alternative measures (some of which are much shorter than the NEO scales) which assess c The ‘NEO Five-Factor Inventory’ (NEO-FFI) and the ‘Revised NEO Personality Inventory’ (NEO-PI-R) are copyright protected; the test materials for paper-and-pencil or computer-based administration are available from Personality Assessment Resources, PAR Inc., 16204 North Florida Avenue, Lutz, FL 33549, USA, and from European suppliers. 51 the same personality domains120,152,153. Validated translations of the NEO measures have also been reported154,155. The NEO personality measures have been extensively used in academic and applied research, including organizational and vocational research140,156,157 and, more specifically, studies of work-related psychosocial risks and health158-160. 5.1.1 Reliability Internal consistency. The NEO-PI-R domain scales show high levels of internal consistency; coefficient alpha values for the self-report scales range from .86 to .92, while for observer ratings, the values range from .89 to .93156. Other authors have also reported good internal consistency for the NEO-PI-R self-report scales160-163. Test-retest reliability. The five NEO scales also show good stability over time; thus, testretest reliability over periods of 6-9 years were found to be above .60106, and a metaanalysis demonstrated a high level of rank order stability over 6.7 years164. In a six-wave study, 6-month test-retest reliabilities for the five scales ranged from .80 to .87, while longer-term reliabilities ranged from .73 to .86162. Agreeableness tended to show the lowest stability, while Openness to Experience had the highest stability. In a further study, over an average 8-year follow-up, NEO-PI-R scores showed high levels of stability in the sample as a whole, although individuals who had experienced a recent traumatic event showed increased Neuroticism (specifically, the ‘angry hostility’ trait)165. 5.1.2 Construct validity Convergent validity. The convergent validity of the NEO scales is demonstrated by the correlations between NEO domain/trait scores and measures of similar constructs. For instance, Costa156 reports correlations of r=.55 and r=.54, respectively, between measures of the NEO anxiety trait (N1) and two other well-established measures of trait anxiety, the Spielberger State-Trait Anxiety Inventory, and the ‘tension’ measure of the Profile of Mood States. Similarly, the NEO trait ‘trust’ (A1) was negatively related (r = -.46) to the suspicion scale of the Buss-Durkee Hostility scale. At the level of higher-order constructs, Rossier et al.166 found that four out of the five NEO-PI-R domains were associated with the corresponding dimensions of the 16 Personality Factors scale (16 PF5); only Agreeableness was not represented in the 16 PF5 item set166. Close convergence between the NEO Neuroticism and Extraversion scales and the corresponding scales of the Eysenck Personality Questionnaire167 has also been reported168,169. Discriminant validity. As evidence of discriminant validity of the NEO measures, Costa156 highlights the contrasting patterns of correlates of different NEO traits in relation to the Jackson Personality Research Form. The discriminant validity of the NEO traits measures has also been evaluated in relation to concurrent and prospective measures of dysfunction in social, work, and recreational domains of life in a large, longitudinal clinical sample. 52 Consistent with theoretical predictions, NEO Neuroticism was broadly related to dysfunction across all domains, Extraversion was primarily related to social and recreational dysfunction, Openness to Experience to recreational dysfunction, Agreeableness to social dysfunction, and Conscientiousness to work dysfunction170. 5.1.3 Concurrent and predictive validity Vocational, behavioural, and psychosocial research has provided evidence of the validity of the NEO measures. Some examples are outlined below. Vocational settings. Several studies demonstrating the concurrent and predictive validity of NEO measures in vocational settings, including selection, training and job performance, are reviewed by Costa156. In a study of the predictive validity of the NEO scales in higher education, Conscientiousness was found to predict academic achievement, while Neuroticism was positively related to performance only under low-stress conditions171. Behavioural studies. NEO traits show the expected correlations with daily behaviours reported over a 30-day period172, and with self-reports of general behaviour patterns173. In a further study, behavioural indicators were assigned a priori to the Big Five dimensions on the basis of theory and expert ratings. These indicators were then assessed in a student sample in a variety of social situations; each of the five personality dimensions predicted actual behaviours in line with the model174. Psychosocial research. Significant associations have been found between NEO scores and work-related psychosocial factors; thus, low Neuroticism together with high Extraversion and high Conscientiousness predicted lower stressor exposure, better physical health, and lower job dissatisfaction175. NEO measures are also important correlates of subjective well-being; Extraversion and Openness to Experience are associated with positive affect, while Neuroticism is strongly linked to negative affect163. In two longitudinal studies, NEO Neuroticism scores significantly predicted the onset of major depression9,159. 5.2 Over-commitment The personality characteristic of over-commitment (OC) describes individual attitudes, behaviours and emotions reflecting excessive work-related striving combined with a need for approval and esteem. This personal coping pattern forms the intrinsic component of the Effort-Reward Imbalance (ERI) model2. The OC dimension was originally designated ‘need for control’, and assessed by means of a 29-item scale with four sub-scales. However, in further studies176,177, the factorial structure of the scale was not successfully replicated, and the scale was unduly long for epidemiological research. Subsequently, exploratory and confirmatory factor analyses were carried out to develop a shorter 6-item scale focusing on items concerned with ‘inability to withdraw from work obligations’75. This OC scale is now routinely used to assess the intrinsic component of the ERI model. 53 The factorial stability of the ERI measures, including the 6-item OC scale, has also been examined; the authors concluded that researchers utilizing the ERI scales “can feel confident that self-reported changes are more likely to be due to factors other than structural change of the ERI scales over time, which has important implications for evaluating job stress and health interventions”76. 5.2.1 Reliability Internal consistency. Coefficient alpha values for the 6-item OC measure were reported from a study of five diverse European samples75. In these samples (ranging in size from N=960 to N=10,174), coefficient alpha was in the range .79 to .82 in both male and female groups, with the exception of one low value (.64) relating to a small group of female transport workers. Other researchers, working with different occupational groups, and using the OC scale in several different European languages, have found values of coefficient alpha in the range .72 - .8123,76,92,178 although occasional higher179 or lower180 values have been reported. Test/retest reliability. De Jonge76 reported test/retest reliability for the OC scale for two samples with different time lags. Over a one-year interval, test/re-test stability was .53, reducing to .45 over two years. The authors note that the test/re-test coefficients assume stability in the work situation, which is rarely the case over extended periods of time. 5.2.2 Validity Convergent validity. Several studies have found significant correlations (in the range .30 to .38) between OC and measures of neuroticism/NA23,92,93. OC was also found to correlate .28 with Type D personality (a combination of high NA and high social inhibition)181. As OC would be expected to include an element of negative affectivity, these findings provide some evidence of the convergent validity of the OC measure. Discriminant validity. Correlations between OC and NEO Five-Factor measures demonstrate discriminant validity; thus, in a cross-sectional sample, OC was found to correlate only weakly with Extraversion (r=.03), Openness (r=.06) and Conscientiousness (r=-.12), both of which represent personality characteristics conceptually very different from OC. Siegrist75 refers to a different form of discriminant validity in noting that mean OC scores differ significantly across major socio-demographic groups. Concurrent and predictive validity. High OC is conceptualised as a maladaptive coping response to demanding work conditions; cross-sectional relationships with measures of impaired health therefore provide indicators of concurrent validity. There is evidence that high OC scores are associated with a wide range of adverse health outcomes, including low self-rated health75, poor psychological well-being and intention to quit among teachers179, adverse physiological responses in men35; exhaustion and impaired health 54 (although not absenteeism)181; high levels of fatigue182, and musculoskeletal pain92. These relationships remained significant when potential confounding variables were controlled. Longitudinal research demonstrates the predictive validity of OC in relation to adverse health outcomes; for instance, high OC predicted poor self-rated health over a one-year period183, the onset of insomnia over a two-year period184, and mental strain among professionals over a 15-month period185. Thus, in relation to health outcomes, the concurrent and predictive validity of the OC scale appears to have been well established. 5.3 Negative affectivity Stable and pervasive individual differences in the tendency to experience negative emotional states, including anxiety, anger, guilt and distress are assessed by measures of neuroticism and negative affectivity. For present purposes, the general term ‘negative affectivity’ (NA) will be used for this personality trait. High NA is associated with emotional vulnerability, pessimism, and a general disposition to react negatively to life and work stressors186; such individuals tend to be worried, easily upset, often moody or depressed, and focused on negative aspects of self, other people, and the world in general. The tendency to focus on negative aspects of self is also reflected in the significant correlations found between NA and self-reported mental and physical health problems, and frequency of health-service use91,94. High NA also predicts long-term ill-health, including all-cause mortality and cardiovascular disease, over extended follow-up periods30,187. Self-report measures of psychosocial stressors, including work-related factors, are also related to NA, leading to suggestions that NA acts as a ‘nuisance’ factor potentially confounding relations between self-reports of psychosocial factors and health outcomes44,45. However, other researchers point to possible substantive mechanisms that could underlie the pattern of relationships shown by NA34,188. 5.3.1 Measures of NA Several measures are currently used for assessing NA traits. They include the Neuroticism measure of the NEO Five-Factor Inventory87 (see Section 4.5), the Eysenck Personality Questionnaire167,189, and the trait NA measure from the State-Trait Anxiety Inventory (STAI)190. These measures are highly inter-correlated168. Two other measures, the Bradburn Affect Balance scale191 and the Positive and Negative Affect Scales (PANAS)192 assess both positive (PA) and negative (NA) affectivity. These two measures differ conceptually. The Bradburn scale consists of five PA items and five NA items, scored dichotomously; positive and negative affect are treated as opposing poles of a single dimension, and the overall ‘affect balance’ score is difference between the PA and NA totals. In contrast, the PANAS scales treat PA and NA as two orthogonal dimensions. In this model, high PA is associated with experiencing positive feelings such as enthusiasm and alertness, whereas low PA is related to feelings of lethargy and sluggishness. Similarly, high levels of NA are associated with negative feelings such as 55 guilt, fear, anxiety, and nervousness, whereas low NA is related to feelings such as serenity and calmness192. The PANAS scales were derived from an initial set of 60 descriptive adjectives193. Starting from this item set, Watson et al. identified and validated 10-item PA and NA scales, made up of relatively ‘pure’ items that had a substantial factor loadings on one factor, but nearzero loadings on the other. The advantages of the PANAS scales (assessment of NA and PA, simplicity, relatively short length, and possibility of using them to assess either traits or short-term states) have led to their widespread application. This section therefore focuses primarily on the reliability and validity of the PANAS scales. 5.3.2 Reliability of the PANAS scales Coefficient alpha values for the PANAS scales were found to range from .84 to .87 ( NA) and from .86 to .90 (PA); in both cases, the alpha values were not markedly affected by the time frame of the assessment192. When administered in the ‘trait’ form (i.e. respondents were asked to report how they generally felt), the NA and PA scales also showed good test-retest reliability (.71 and .68 respectively) over an eight-week interval. More recent data confirm the high reliability of PA and NA194,195, and a shortened version with 5-item scales was also found to show good reliability196. 5.3.3 Validity of the PANAS scales Convergent and discriminant validity. Watson et al.192 reported relatively low intercorrelations of the NA and PA, ranging from -.12 to -.23 across different time frames, although a later confirmatory factor analysis indicated a correlation of -.30 between the latent factors for NA and PA194. Both the PANAS scales demonstrated good convergent validity with similar measures devised in the Netherlands197. In relation to other trait measures, the PANAS scales were found to correlate with the measures from the NEO Five-Factor Inventory; PA correlated .61 with extraversion and .55 with neuroticism, while NA correlated -.72 with neuroticism and -.31 with extraversion195. In this study, NA and PA also showed patterns of significant relationships with other personality variables. In particular, PA was strongly positively related to selfesteem (.75) and self-efficacy (.65), while NA was negatively related (-.50 and -.48, respectively) to these traits, thus raising some issues of discriminant validity. Concurrent and predictive validity. Several studies have demonstrated the validity of the trait form of the PA and NA measures in relation to health and work-related outcomes: • PA was positively related to job satisfaction, both concurrently (r = .45) and predictively over a six-month period (r = .34); NA was significantly negatively related to job satisfaction (r = -.20, concurrently, and r=-.24, predictively)195. 56 • Denollet et al.197 found significant negative correlations between NA and measures of mental health, physical health, social relationships, and personal competence, together with significant positive correlations of NA with perceived stress, depressive symptoms, emotional exhaustion, and fatigue. PA showed relationships in the opposite direction and generally smaller in magnitude. Similar findings have been reported from a separate study198. • A meta-analytic study of PA and NA in work settings demonstrated that, as predicted, NA was positively related to withdrawal behaviours, counterproductive work behaviours, and occupational injury, while PA was a positive predictor of organizational citizenship behaviours and task performance199. This study also showed that extraversion and neuroticism measures did not contribute to explaining task performance over and above the effects of NA and PA. • Using a Dutch version of the PANAS scale, and a two-wave panel design, Houkes et al. found that NA predicted increase in emotional exhaustion over a one-year period78. • In two prospective studies, trait NA (assessed by the ‘Bradburn Affect Balance’ scale) predicted incident coronary heart disease over a mean follow-up period of 11-12 years after control for a range of demographic, physiological, and lifestyle factors200,201. 5.4 Hostility Type A behaviour pattern (TABP) has long been recognized as a risk factor for coronary heart disease and other health problems; however, of the two main components that make up TABP (time urgency, and aggression/hostility), evidence suggests that hostility is the ‘toxic’ factor underlying health risks29,66,202. This review therefore focuses on the reliability and validity of hostility measures, rather than measures of overall TABP. Hostility is a multi-faceted construct, incorporating an affective component (anger, annoyance, resentment and contempt), a cognitive component (cynicism and negative beliefs about human nature in general), and a behavioural component (aggression, antagonism, and uncooperativeness). However, these components are not always distinguished clearly in measures of hostility, leading to ambiguity in interpreting scale scores. Nonetheless, hostility has been identified as an important risk factor for a range of physical health problems and for all-cause mortality79,202,203. The main features and psychometric properties of two widely-used measures of hostility (the Buss-Durkee scale, and the Cook-Medley Scale) together with a short 3-item scale (Finnish Twin Study scale) are summarised below. 57 5.4.1 Buss-Durkee Hostility Inventory The Buss-Durkee Hostility Inventory (BDHI)204 is the longest-established measure of hostility; it also has the most items (75 true/false statements) from which eight subscales (‘assault’, ‘verbal hostility’, ‘indirect hostility’, ‘irritability’, ‘negativism’, ‘suspicion’, ‘resentment’ and ‘guilt’) are derived. The BDHI scale has been used in a variety of studies101,205,206, but it is too long for most epidemiological research. It has also been criticised on psychometric grounds; although the total score has an acceptable internal consistency (mean alpha value = .82 ± .11)207, the subscales tend to have low alpha values205,208. The test-retest reliability over a two-week period was found to be .64208. Convergent and discriminant validity. Factor analysis of the BDHI items has identified two separate sub-scales, ‘expressive hostility’ (or ‘overt aggression’), and ‘neurotic hostility’ (or ‘covert aggression’), respectively209,210, both of which have good reliability209. In relation to the NEO Five-Factor Personality Inventory, ‘neurotic hostility’ is strongly related to Neuroticism, r = .66 (men) and r = .63 (women), while ‘expressive hostility’ is negatively related to Agreeableness, r = -.57 (men) and -.51 (women)211. The correlations of the hostility factors with NEO scores for Openness and Extraversion were low and non-significant. Thus, there is evidence for the convergent and discriminant validity of the two factors of the BDHI. Concurrent and predictive validity. Evidence of the concurrent and predictive validity of the BDHI scales in relation to physical illness, including cardiovascular disease, is reviewed by Smith29. Other relevant findings include significant cross-sectional relationships between specific BDHI subscales and symptoms of anti-social and borderline personality disorders in non-clinical groups205. Prospectively, the BDHI ‘neurotic hostility’ factor predicted all-cause mortality over a 12-year period in a fullyadjusted model, including control for other personality factors212, and the BDHI total predicted increase in depression over a three-year period101. 5.4.2 Cook-Medley scale The Cook-Medley hostility scale (Ho)213 is a 50-item true/false scale derived from the Minnesota Multiphasic Personality Inventory (MMPI); it is generally regarded as a measure of ‘cynical hostility’ assessing anger-proneness, resentment, cynicism, and mistrust towards others. The original Ho scale has acceptable internal consistency (reported alpha values of .77208 and .8446), but the relatively high correlation between Ho scores and NA may confound interpretation of findings. For instance, control for NA markedly reduced the correlation between Ho scores and psychosocial measures46. These findings suggest that NA should be controlled when using the Ho scale in psychosocial research. Factor analyses of the Cook-Medley scores revealed a strong single factor, but also evidence of additional small, unstable factors214. Using a more sophisticated form of factor analysis, Strong et al.215 identified 17 items that reflected hostile attitudes and expectations 58 of a hostile world. The 17-item scale total correlated highly with the 50-item Ho scale, and (unlike the 50-item scale) was not differentially influenced by gender. The 17-scale has been reported to have good reliability (α = .82), to correlate with other measures of hostility, and to predict responses to a laboratory stressor216. High scores on the scale are associated with depressive symptoms and negative affect but not with positive affect216. Thus, there is some evidence of convergent and discriminant validity for the 17-item Cook-Medley scale. There is also evidence of the predictive validity of the 50-item Cook-Medley total score. In a large sample of women, those with scores in the top quartile of the scale had significantly higher rates of heart disease at 8-year follow-up relative to those in the lowest quartile217 and, in a separate 8-year follow-up study, total scores were predictive of poorer pulmonary function and more rapid rates of decline among older men. 5.4.3 Finnish Twin Study Scale of Hostility Reliability. The ‘Finnish Twin Study Scale of Hostility’218 has only three items. Short scales tend to have lower reliability, and the value of coefficient alpha (.63) for this scale77 falls below the normally acceptable level. Nonetheless, the brevity of the scale offers advantages in large-scale survey research. A test-retest correlation of .57 over a nine-year period indicates that the scale has satisfactory temporal stability219. Construct validity. The scale has shown convergent validity in significant correlations with Spielberger’s Trait-Anger scale (r=.62 for women, r = .71 for men)219, and it has shown predictive validity in relation to sickness absence, hospitalization, coronary heart disease, and mortality218-220. 5.5 Sense of coherence ‘Sense of Coherence’ (SOC) is the central construct in Antonovsky’s salutogenic theory which seeks to understand “how people manage stress and stay well”126. SOC is defined as “A global orientation that expresses the extent to which one has a pervasive, enduring though dynamic feeling of confidence that (1) the stimuli deriving from one’s internal and external environments in the course of living are structured, predictable, and explicable; (2) the resources are available to one to meet the demands posed by these stimuli; and (3) these demands are challenges, worthy of investment and engagement”42. These three components of SOC reflect individual beliefs about the ‘comprehensibility’, ‘manageability’, and ‘meaningfulness’ of events and experiences in life. Although the three components reflect different aspects of the SOC orientation, the scale was designed to assess a global orientation, rather than three subscales42. The original SOC scale had 29 items, but a 13-item version has also been developed42,221. The SOC scales have been widely used, although the majority of published work originates from Finland and other Scandinavian countries. Consistent with Antonovsky’s theory, SOC measures have primarily been applied in studies of stress, coping and health. 59 5.5.1 Reliability Internal consistency. In an exhaustive review of SOC measures, coefficient alpha was reported to range from .70 to .95 for the 29-item scale, and from .70 to .92 for the 13-item scale128. More recent work also finds coefficient alpha values in these ranges86,131. Thus, internal consistency values are good or very good. A 3-item scale, with one item for each of the SOC components, has also been reported222,223, but there appears to be no information about alpha values for this scale. Test-retest reliability. As reviewed by Eriksson and Lindström128, test-retest reliabilities for the 29-item SOC scale range from .92 (over one week) to .77 (over six months). Over similar time periods, the 13-item SOC had slightly lower values. Longer time periods are associated with lower test-retest values; for instance, .63 over a three-year period224. Antonovsky considered that an individual’s level of SOC would be fully developed and stable by age 30 years42. Some findings support the view that the temporal stability of SOC scores is greater among those age 30+ years as compared with a younger groups225 although, in an earlier study, age was not found to play any role in the stability of SOC127. Moreover, other evidence suggests that SOC tends to increase with age throughout the whole life span128. The many discrepant findings have led to extensive debate about the temporal stability of the SOC scale. In a further contribution, Smith et al. suggested that SOC measures incorporate both a stable ‘trait’ component and a changeable ‘state’ component, and cautioned against using SOC to represent a stable disposition96. This view is consistent with findings indicating that SOC acts as a mediator of relations between psychosocial stressors and health outcomes43. 5.5.2 Construct validity Convergent and discriminant validity. The role of SOC as a health-promoting individual characteristic suggests that convergent validity should be shown by positive correlations between SOC scores and personality measures reflecting adaptability and good coping skills, and negative correlations with measures of neuroticism/NA. Some relevant evidence has been reported. For instance, SOC scores are positively correlated with a combined measure of autonomy, adaptability, and psychological functioning226, and with frustration tolerance227. Strong positive correlations with self-esteem and optimism have also been reported128. The strongly negative association of SOC scores with trait anxiety (-.85)221, and with neuroticism (-.85)86, provides further evidence of convergent validity. Several other researchers have also drawn attention to the high negative relationships between SOC and measures of negative affectivity227,228. These findings raise questions about discriminant validity of SOC relative to NA, and the extent to which SOC and NA contribute independently to the prediction of measures of mental and physical health. 60 The relatively modest correlations between SOC scores and measures of extraversion86,227, and other NEO Five Factor scales86 provide some evidence of discriminant validity. However, Frenz et al.221 noted that SOC scores were significantly positively correlated with social desirability, and concluded that evidence for the discriminant validity of the SOC measures was mixed. In a further study229, in which social desirability was controlled, SOC scores were found to show significant partial correlations with dispositional measures and with measures of adaptive coping behaviours. Thus, the discriminant validity of the SOC scale is less well-established than its convergent validity. Concurrent and predictive validity. SOC scores are associated, both concurrently and predictively, with a wide range of health-related outcomes. For instance, SOC scores are higher in non-clinical as compared with clinical groups221; SOC correlates negatively with depression (r=−0.49) and anxiety (r=−0.52)226; and, in employed groups, high SOC scores are related to lower rates of sickness absence230, and to greater ability to cope with job demands231. High SOC is also associated, in favourable directions, with a range of health behaviours such as diet, exercise, and smoking habits232,233. Prospective studies demonstrate the predictive validity of SOC scores in relation to health. For instance, baseline SOC predicted all-cause mortality at 6-year follow-up, independent of age, sex, and chronic disease; this result remained significant after control for other variables, including hostility and NA223. Mastery and SOC scores were also found to contribute independently to the prediction of mortality234. Over a shorter follow-up period (one year), SOC predicted physical and mental health outcomes after control for demographic factors and initial health status235. In both these studies, the effect of SOC was significant over and above the effects of NA. Other prospective studies227,236,237 also illustrate the role of SOC as a protective factor that mitigates the adverse effects of life and work stress. 5.6 Locus of control The locus of control (LOC) construct refers to the extent to which individuals believe that outcomes are determined by personal effort and ability (internal control) rather than by outside influences such as fate, chance, and powerful others (external control). The original LOC measure, devised by Rotter238, was intended for use with students. Scales which are more suited to general population samples, have better psychometric properties, and may incorporate several subscales, have been developed subsequently82,239,240; other LOC scales focus on specific life domains, such as work83. The LOC construct has also been incorporated into measures assessing broader personality constructs, such as hardiness (challenge, commitment, and control)241 and, more recently, ‘Core Self Evaluations’242. A 1993 critique of some 50 different LOC measures reviews conceptual and methodological issues in the assessment of control beliefs, including dimensionality, domain specificity, and scale reliabilities243. 61 In general, internal LOC is positively associated with adaptive personality traits, such as extraversion, sense of coherence, self-esteem, and self-efficacy, and negatively associated with neuroticism and other NA measures244,245; internal control is also associated with use of adaptive coping responses246-248, with more effective work functioning249 and, in a 7year prospective study, with lower risk of incident psychological distress250. 5.6.1 ‘Spheres of Control’ scale The ‘Spheres of Control’ scale (SC)240 provides an example of the development and psychometric evaluation of a multi-dimensional LOC measure. The 30-item scale assesses control beliefs in three activity domains240,251: in the non-social environment, in the form of efficacy and achievement (personal control), in dyadic relationships and social groups (interpersonal control), and in society more generally (socio-political control). The three domains are seen as conceptually independent; empirically, the scale inter-correlations are low to moderate244,252,253. Reliability. For the interpersonal and socio-political scales, alpha values are generally in the acceptable range251,254. However, the original personal control scale had low reliability251,252, and was subsequently revised251. Test-retest reliability for the scale total was found to be .80 after a four-week interval, and .60 after six months251. Convergent and discriminant validity. The three SC scales show good convergent validity with similar constructs assessed by other LOC measures; for instance, the personal control scale is related to other measures of internality and self-efficacy; the interpersonal scale is related to interpersonal competence, and the socio-political scale is related to a measure of a ‘politically responsive world’251. The subscales are also correlated in predictable ways with trait measures, such as extraversion, self-esteem, and neuroticism244,252. Concurrent and predictive validity. Several studies have demonstrated the concurrent validity of the SC scales in psychosocial research. Thus, external interpersonal control was associated with role ambiguity254; external personal control was significantly related to self-reports of worry about life stressors255; and internal personal and interpersonal control predicted life satisfaction256. In work contexts, internal personal control was found to be negatively related to voluntary union membership257, and positively related to willingness to act as a mentor258. Also, in a longitudinal diary study, interpersonal control was found to predict adaptive coping behaviours and emotional reactions to conflict259. 5.7 Core Self Evaluations scale ‘Core Self Evaluations’ (CSE) is described as a higher-order construct representing an individual’s fundamental beliefs about his or her own competence and self-worth242. The CSE measure combines four traits, emotional stability, locus of control, general selfefficacy, and self-esteem; although these traits have traditionally been regarded as separate, evidence suggests that they can be represented by a single latent factor260. The development of this scale is relatively recent and it was not used in any of the studies 62 reviewed in Section 2, but it has been shown to have potential application in work stress research and its psychometric characteristics are therefore briefly considered here. The development and validation of a 12-item CSE measure, and its relationships to other personality constructs, has been reported by Judge et al.242,260,261. The alpha reliability value was found to be .84, and test-retest reliability over three months was .81242. The CSE total correlates highly with measures of each of the component traits, particularly the Neuroticism measure from the NEO Five Factor inventory. Other NEO scales, are moderately (Conscientiousness and Extraversion) or weakly (Agreeableness and Openness) correlated with CSE scores242. Thus, the CSE scale shows convergence with related traits, and divergence from measures of different constructs. Substantial evidence, including longitudinal findings262-265 has accumulated to demonstrate that individuals with high CSE scores perceive fewer stressors and use more effective coping strategies265,266, are less likely to experience burnout in stressful work environments267, are more successful at work263,268, report higher job satisfaction269, and are more able to recover from job loss264. These results suggest that the CSE measure has good concurrent and predictive validity in occupational settings. However, in relation to measures of stress, strain and depression, neuroticism was found to account for significant incremental variance (10%) over and above the CSE measure260. Thus, although CSE is seen as representing a broad, inclusive measure of emotional stability270, in the context of stress research, use of a specific NA trait measure potentially provides additional information over and above that attributable to CSE. The CSE scale has also been used with measures from the job strain and effort-reward models to predict health-related outcomes. CSE was found to be a stronger predictor of reported job stress than the demand, control, and support variables of the job strain model271 and, in a longitudinal study based on the ERI model, CSE was a significant predictor of emotional exhaustion over and above the effects of baseline measures and ERI at follow-up262. The CSE measure has been described as particularly well-suited to stress research265,271. The findings outlined above (good reliability and validity, relatively short length, and its significant role in relation to stress, coping and health) tend to confirm this view, although the role of NA in explaining incremental variance, over and above the CSE measure, in predicting stress-related outcomes should not be disregarded. 5.8 General issues The sections above summarise the psychometric properties of a range of measures that assess personality characteristics known to be implicated in the pathways by which workrelated psychosocial risk factors give rise to adverse health outcomes. There are of course other personality factors not included in the present review that also play significant roles in the stress process. However, the five personality variables considered in detail here (over-commitment, negative affectivity, hostility, sense of coherence, and locus of 63 control), together with the NEO Five-Factor model dimensions, accounted for the great majority of the significant findings in the systematic review of prospective studies described in Section 2. Several general points emerge from the material considered: • Whilst most of the measures described have adequate internal consistency, as assessed by coefficient alpha, there is a trade-off between scale length and coefficient alpha values. Longer scales tend to have higher alpha values, but they are less suitable for large-scale survey research because of the time required to complete the items. Thus, short 3-item versions of longer scales (e.g. hostility and SOC) were successfully used by some researchers in place of the original measures, in spite of the relatively low alpha values for these scales. Irrespective of the particular scale selected, it is important that coefficient alpha values are reported for the data set concerned. • Evidence of the convergent and discriminant validity of the scales reviewed shows that over-commitment, hostility, sense of coherence (SOC) and locus of control are significantly correlated (either positively or negatively) with NA. The negative correlation with NA is particularly high for the SOC measure. These findings raise questions about the extent to which other personality measures, moderately or highly correlated with NA, contribute independently to health-related outcomes when evaluated jointly with NA in simultaneous analysis models. The prospective studies reviewed in Section 2 provide little information on this point. Although nine studies included one or more personality variables in addition to a measure of NA, there were only three instances in which the other personality variables contributed significant incremental variance. Thus, over and above the effects of NA, hostility predicted sickness absences77; SOC predicted physical health235, and extraversion predicted voluntary turnover272. In addition, research not included in the present review provides some further evidence of the independent effects of SOC and NA on health outcomes223. • As discussed in Section 3, there is evidence that not only mean-level change in personality occurs over the life-course, but also that work experiences may result in personality change. Thus, personality measures cannot be regarded as entirely stable over extended periods of time, or even in some instances (e.g. SOC) over time periods as short as one year. The implication is that in prospective studies including personality variables, the measures should be repeated at each wave of data collection, rather than only used at baseline. 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International Archives of Occupational and Environmental Health, 82, 1005-1013. 80 Appendix To illustrate the nature of the measures described in this report, some of the scales reviewed are reproduced here, with details of scoring systems, when available. Over-commitment (OC) scale 1. I get easily overwhelmed by time pressures at work. 2. As soon as I get up in the morning I start thinking about work problems. 3. When I get home, I can easily relax and ‘switch off’ work. 4. People close to me say I sacrifice too much for my job. 5. Work rarely lets me go, it is still on my mind when I go to bed. 6. If I postpone something that I was supposed to do today I’ll have trouble sleeping at night. Items are scored on a 1-4 Likert scale, ranging from 1= ‘Strongly disagree’ to 4 = ‘Strongly agree’. The six items are summed to form a total score ranging from 6 - 24. The higher the score, the more likely a subject is to experience over-commitment at work. Source: Siegrist et al.(2009)273 81 Positive and negative affect scales (PANAS) Source: Watson et al. (1988)192 This scale consists of a number of words that describe different feelings and emotions. Read each item and then mark the appropriate answer in the space next to that word. Indicate to what extent (INSERT APPROPRIATE TIME INSTRUCTION HERE). Use the following scale to record your answers: 1 = very slightly or not at all 2 = a little 3 = moderately 4 = quite a bit 5 = extremely ___________ interested* ___________ irritable ___________ distressed ___________ alert* ___________ excited* ___________ ashamed ___________ upset ___________ inspired* ___________ strong* ___________ nervous ___________ guilty ___________ determined* ___________ scared ___________ attentive* ___________ hostile ___________ jittery ___________ enthusiastic* ___________ active* ___________ proud* ___________ afraid * Items marked with an asterisk assess PA; the remaining items assess NA PANAS has been used with the following time instructions: Moment (you feel this way right now, that is, at the present moment) Today (you have felt this way today) Past few days (you have felt this way during the past few days) Week (you have felt this way during the past week) Past few weeks (you have felt this way during the past few weeks) Year (you have felt this way during the past year) General (you generally feel this way, that is, how you feel on average) 82 Eysenck Personality Questionnaire, EPQ-R Source: Eysenck, Eysenck & Barrett (1985)167 Instructions. Please answer each of the questions below by putting a circle around the "YES" or the "NO to indicate the response which is true, or most often true, of yourself. There are no right or wrong answers, and no trick questions. Work quickly and do not think too long about the exact meaning of the questions. N Does your mood often go up and down? YES NO E Are you a talkative person? YES NO N Do you ever feel 'just miserable' for no reason? YES NO E Are you rather lively? YES NO N Are you an irritable person? YES NO E Do you enjoy meeting new people? YES NO N Are your feelings easily hurt? YES NO E Can you usually let yourself go and enjoy yourself at a party? YES NO N Do you often feel 'fed up'? YES NO E Do you usually take the initiative in making new friends? YES NO N Would you call yourself a nervous person? YES NO E Can you easily get some life into a rather dull party? YES NO N Are you a worrier? YES NO E Do you tend to keep in the background on social occasions? YES NO N Would you call yourself tense or 'highly-strung'? YES NO E Do you like mixing with people? YES NO N Do you worry too long after an embarrassing experience? YES NO E Do you like plenty of bustle and excitement around you? YES NO N Do you suffer from nerves? YES NO E Are you mostly quiet when you are with other people? YES NO N Do you often feel lonely? YES NO E Do other people think of you as being very lively? YES NO N Are you often troubled about feelings of guilt? YES NO E Can you get a party going? YES NO KEY E = Extraversion items N = Neuroticism items (Items on other EPQ-R scales are not included in the list above) The bold response for each item is scored 1. Other responses are scored 0. 83 Cook-Medley Hostility scale 17-item version. Source: Strong et al. (2005)215 Items are scored on a true/false basis People use unfair means for gainsb I’m on guard with friendly people I am more competent than my bossb Pleased when others punished Many are guilty of bad conductb Boss takes all credit and no blame I am impatient when interruptedb Often disappointed by others Difficult to convince others of the truthb My behaviour is often misunderstood Inwardly dislike helping othersb Go out of my way to win an argument Question motives of helpful people Others are honest to avoid punishmentb Others can tell what I’m thinking Friends are only there to be usedb I enjoy keeping others guessing Others are jealous of my ideasb b These items form an alternative 9-item scale Finnish Twin Study Scale of Hostility Source: Elovainio et al, (2003)77 Instructions. Answer according your real self-opinions, not according your ideal or other peoples opinion. Use the extremes when appropriate, and circle the middle line only in a case when it really best indicates your character. Scoring 1 2 3 4 5 6 7 Seldom get into into arguments — — — — — — — Prone to get into arguments easily Do not get angry easily — — — — — — — Get angry easily Get irritated easily — — — — — — — Do not get irritated easily The hostility score is the average of the three item scores. Coefficient alpha =.63 84 Sense of coherence scale (SOC)42 13-item version. Source: Smith et al (2003)96 Items are scored on a 7-point Likert scale; response scales are shown for each item. 1. How often do you have a feeling that you don’t really care about what goes on around you? (1=very seldom or never, 7=very often)* 2. How often in the past were you surprised by the behaviour of people whom you thought you knew well? (1=never happened, 7=always happened)* 3. How often have people you counted on disappointed you? (1=never happened, 7=always happened)* 4. How often do you have the feeling you’re being treated unfairly? (1=very often, 7=very seldom or never) 5. How often do you have the feeling you are in an unfamiliar situation and don’t know what to do? (1=very often, 7=very seldom or never) 6. How often do you have very mixed up feelings and ideas? (1=very often, 7=very seldom or never) 7. How often do you have feelings inside that you would rather not feel? (1=very often, 7=very seldom or never) 8. Many people – even those with a strong character – sometimes feel like losers in certain situations. How often have you felt this way in the past? (1=very seldom or never, 7=very often)* 9. How often do you have the feeling that there’s little meaning in the things you do in your daily life? (1=very often, 7=very seldom or never) 10. How often do you have feelings that you’re not sure you can keep under control? (1=very often, 7=very seldom or never) 11. Until now has your life had no clear goals or purpose, or has your life had very clear goals and purpose? (1=no clear goals and purpose, 7=very clear goals and purpose) 12. When something happens, you generally find that you overestimate or underestimate its importance or do you see things in the right proportion? (1=overestimate or underestimate its importance, 7=see things in the right proportion) 13. Is doing the things you do every day a source of great pleasure and satisfaction or a source of pain and boredom? (1=a great sense of pleasure and satisfaction, 7=a source of pain and boredom)* * Five of the 13 questions are reversed-scored, giving a total score ranging from 13 to 91; the higher the score, the greater the sense of coherence. 85 Sense of Coherence (3-item version) Source: Lundberg et al. (1995)222 Manageability (1) Do you usually see a solution to problems and difficulties that other people find hopeless? Yes, usually Yes, sometimes No 2 1 0 Meaningfulness (2) Do you usually feel that your daily life is a source of personal satisfaction? Yes, usually Yes, sometimes No 2 1 0 Comprehensibility (3) Do you usually feel that the things that happen to you in your daily life are hard to understand? Yes, usually Yes, sometimes No 2 1 0 86 Personal Control / Mastery scale Source: Pearlin et al. (1981)82 1=strongly agree 5=strongly disagree How strongly do you agree or disagree that: 1. I have little control over the things that happen to me 1 2 3 4 5 2. Sometimes I feel that I’m being pushed around in life 1 2 3 4 5 3. There is really no way I can solve some of the problems I have 1 2 3 4 5 4*. I can do just about anything I really set my mind to 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 5. I often feel helpless in dealing with the problems of life 6*. What happens to me in the future mostly depends on me 7. There is little I can do to change many of the important things in my life * Indicates a reverse-scored item Version used by Marchand et al (2005) 250 and by Wickrama et al. (2009)85 87 Core Self Evaluations Scale Source: Judge et al. (2003)242 Instructions: Following are several statements about which you may agree or disagree. Using the response scale provided, indicate you agreement or disagreement with each item by putting the appropriate number on the line preceding that item. 1 = Strongly disagree 2 = Disagree 3 = Neutral 4 = Agree 5 = Strongly agree _______ I am confident I get the success I deserve in life _______ Sometimes I feel depressed ** _______ When I try, I generally succeed _______ Sometimes when I fail, I feel worthless ** _______ I complete tasks successfully _______ Sometimes I do not feel in control of my work ** _______ Overall, I am satisfied with myself _______ I am filled with doubts about my competence ** _______ I determine what will happen in my life _______ I do not feel in control of my success in my career ** _______ I am capable of coping with most of my problems _______ There are time when things look pretty bleak and hopeless to me ** ** These items are reverse scored