Synergistic interaction between job control and social support at work on depression, burnout, and insomnia among Japanese civil servants.

PURPOSE: To elucidate whether low job control and low social support at work have synergistic interaction on mental health. The synergistic interaction was also analyzed after stratification by high and low job demands.
METHODS: Participants were 2,121 local government employees in Asahikawa city, Japan. The Brief Job Stress Questionnaire was used to assess job demands, job control, and social support. Depression was assessed using the Patient Health Questionnaire-9. The Maslach Burnout Inventory-General Survey was used to assess burnout. Insomnia was assessed using the Athens Insomnia Scale. Possible confounder-adjusted logistic regression analyses were performed to obtain odds ratios for depression, burnout, and insomnia, and synergy indices between job control and social support at work were assessed.
RESULTS: The synergy indices among men and women, respectively, were 2.08 (80 % confidence interval: 1.01, 4.27) and 1.98 (0.67, 5.89) for depression, 1.79 (1.28, 2.51) and 2.62 (1.07, 6.40) for burnout, and 1.92 (1.22, 3.02) and 2.77 (0.43, 18.01) for insomnia. Men with high job demands had higher synergistic interaction on depression and burnout, compared to men with low job demands, and women with low job demands had higher synergistic interaction between job control and social support at work on burnout and insomnia, compared to women with high job demands.
CONCLUSIONS: There were more-than-additive interactions of job control and social support at work on depression, burnout, and insomnia. After stratification by job demands, the synergistic interaction may be different between men and women. To assess job stress, it is necessary to consider the interactive effect of not only job demands and job control but also job control and social support at work.