Effect modification by workplace social capital on the association between depression and workplace and family stress: the Japanese civil servant study

Background: Mental health problems among workers have become an issue in Japan. The working environment for civil servants is becoming excessively stressful, and there is a need to prevent the onset of depression. In addition to stress at the workplace and at home, social capital has been reported as a factor associated with depression. This study examined whether workplace social capital reduces the association between depression and work-related stress or depression and home-related stress. Methods: A total of 3015 Japanese civil servants (1867 men and 1148 women) from Toyama Prefecture were included in this study. Data on depression and workplace social capital, work status, work stress, work–life balance, and physical health were collected. Results: The odds ratio for depression was higher for both men and women with low workplace social capital. For those with low workplace social capital, the adjusted odds ratio for depression was 2.93 (95% confidence interval [CI], 2.16–3.98) for men and 2.46 (95% CI, 1.74–3.49) for women. After adjusting for workplace social capital, the associations between depression and low job position, low job support, and moderate family–to–work conflict declined in men and were no longer significant. For women, the strength of the association between depression and unmarried status along with moderate control at work decreased and also lost significance. When the ORs for depression were stratified by high and low workplace social capital and compared with the ORs before stratification, the ORs for depression of long working hours and work–to–family conflict increased for both men and women in the low workplace social capital group. Conclusions: Workplace social capital mitigated the effect of workplace and family stress leading to depression in both men and women.