Job strain as a risk factor for clinical depression: systematic review and meta-analysis with additional individual participant data.

BACKGROUND: Adverse psychosocial working environments characterized by job strain (the combination of high demands and low control at work) are associated with an increased risk of depressive symptoms among employees, but evidence on clinically diagnosed depression is scarce. We examined job strain as a risk factor for clinical depression. METHOD: We identified published cohort studies from a systematic literature search in PubMed and PsycNET and obtained 14 cohort studies with unpublished individual-level data from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium. Summary estimates of the association were obtained using random-effects models. Individual-level data analyses were based on a pre-published study protocol. RESULTS: We included six published studies with a total of 27 461 individuals and 914 incident cases of clinical depression. From unpublished datasets we included 120 221 individuals and 982 first episodes of hospital-treated clinical depression. Job strain was associated with an increased risk of clinical depression in both published [relative risk (RR) = 1.77, 95% confidence interval (CI) 1.47-2.13] and unpublished datasets (RR = 1.27, 95% CI 1.04-1.55). Further individual participant analyses showed a similar association across sociodemographic subgroups and after excluding individuals with baseline somatic disease. The association was unchanged when excluding individuals with baseline depressive symptoms (RR = 1.25, 95% CI 0.94-1.65), but attenuated on adjustment for a continuous depressive symptoms score (RR = 1.03, 95% CI 0.81-1.32). CONCLUSIONS: Job strain may precipitate clinical depression among employees. Future intervention studies should test whether job strain is a modifiable risk factor for depression.

Occupational burnout and chronic work disability: an eight-year cohort study on pensioning among Finnish forest industry workers.

BACKGROUND: The objective was to explore if burnout, a syndrome from chronic work stress, predicts work disability during eight years among industrial employees. We investigated whether burnout would predict disability in initially healthy employees and all subgroups by the most common causes for disability. METHODS: Of the participants in a company-wide survey (n=9705, 63%) performed in 1996, 8371 employees were identified and 7810 provided full information. The impact of burnout and its sub-dimensions, assessed with the Maslach Burnout Inventory-General Survey, on being granted register-based new disability pension till 2004 was analysed with Cox hazard regression and multinomial regression. The analyses were adjusted for socio-demographic factors, registered medication use, and self-reported chronic illness at baseline. RESULTS: The hazard ratio (HR) for new disability pension was 3.8 (95% confidence interval CI 2.7-5.4) with severe burnout. The risk of severe burnout and severe exhaustion for work disability attenuated but remained significant after adjustments. The association between severe burnout and work disability was significant also in the subpopulation of employees without registered medication at baseline but not among employees healthy by self-report. Crude associations between burnout and all categories of cause-specific disability were significant. The exhaustion dimension predicted work disability due to mental and miscellaneous disorders after adjustments. LIMITATIONS: A non-random one-branch sample was used. The final sample covered 50% of eligible employees. CONCLUSIONS: In industrial work, burnout-related chronic work disability is general in nature. Burnout predicts work disability among healthy employees when health is assessed with registered use of medication but not when it is determined by self-report.