Psychosocial factors at work and risk of depression: a systematic review of the epidemiological evidence

OBJECTIVES: Major depression is a leading cause of psychiatric morbidity and may be influenced by psychosocial factors in the workplace, although evidence so far remains circumstantial. This paper reviews follow-up studies addressing the risk of major depression and depressive symptoms relative to psychosocial stressors in the working environment and evaluates the evidence for causality. METHOD: Follow-up studies were identified by a systematic Medline search combining search terms for the outcome and measures of job-related psychosocial factors. The quality of the studies was evaluated using 22 criteria related to their potential for bias and confounding. RESULTS: Sixteen company or population-based studies including some 63,000 employees were identified. Validated multi-item scales were used to measure perceived psychosocial stressors in most of the studies. Major depression was defined by clinical criteria in seven studies and by symptom scales in another seven. The follow-up period ranged from 1 to 13 years. The prevalence of depressive disorder varied substantially, suggesting a high degree of study heterogeneity. The adjusted relative risk for onset of a major depressive episode according to job stressors ranged from 0.5 to 1.5 in 44 of 61 reported associations with various psychosocial factor dimensions. Associations were strongest and most consistent for job strain defined as high demand and low decision latitude among men. Most studies shared common limitations such as lack of independent measures of exposure and outcome and potential confounding. Although a meta-analysis would technically be possible, heterogeneity across studies evidenced by variation in the prevalence of depression made this unfeasible. CONCLUSION: This review provides consistent findings that perception of adverse psychosocial factors in the workplace is related to an elevated risk of subsequent depressive symptoms or major depressive episode; however, methodological limitations preclude causal inference. Studies implementing objective measures of job stressors or independent outcome ascertainment are warranted.