There seems to be little agreement on relationship between mental health status and overtime work. The present study was therefore conducted in order to determine whether depression status is affected by overtime work or job stress. Participants in this study were 805 full-time non-shift employees (mean age : 39.2±9.6 years) of a manufacturing company in Japan. Participants completed self-administered questionnaires comprised of sociodemographic and lifestyle items. In addition, participants completed the Japanese version of the Job Content Questionnaire and the Center for Epidemiological Studies-Depression Scale. Questionnaire data indicated that 293 (36.4%) participants had depression. Sociodemographic and lifestyle factors that were significantly associated with depression according to χ2 tests were age, marital state, exercise habits, sleeping duration, job stress, job support from supervisors or coworkers, physical load, and postural load. In stepwise logistic regression analysis, high strain jobs were more likely to be significantly associated with depression than active jobs. Furthermore, lack of job support from supervisors or coworkers and high postural load were more common among participants with depression. No significant association was observed between depression and overtime working. In high strain jobs, overtime work was significant associated with depression ; however, this association was not observed for low strain, passive, or active jobs. Among the participants with a high strain jobs, odds ratio for depression of more than 60 hours overtime working per month was 10.14 (95%CI, 2.22-46.35) as compared with less than 30 hours overtime working per month in stepwise logistic regression analysis. In conclusion, overtime work was found to be associated with increased risk of depression for employees characterized as having high strain jobs.
