Long working hours and depressive symptoms: moderation by gender, income, and job status

Background: Long working hours can be a risk factor for poor mental health; however, little is known about the potential factors moderating their relation. This study investigates the association between working hours and depressive symptoms, and explores the potential moderating effect of gender, income level, and job status on this association using a nationally representative sample of working population in South Korea. Methods: Data of 7,082 workers aged 19 years or above were obtained from the Korea National Health and Nutrition Examination Surveys (KNHANES) conducted in 2014, 2016, and 2018 in South Korea. Working hours were categorized into 35–39, 40, 41–52, 53–68, and ≥69 hours/week. Depressive symptoms were evaluated using the Patient Health Questionnaire-9 (PHQ-9). Results: Individuals working ≥69 hours/week were more likely to have moderate to severe depressive symptoms compared to those working 40 hours/week. The association between longer working hours and depressive symptoms was especially prominent in female workers, standard wage workers, and workers with low income levels. We observed significant partial mediation pathways between working hours and PHQ-9 scores through both perceived usual stress level and self-rated health in the total sample. Limitations: The cross-sectional design of the study limits causal interpretation of the findings. Conclusion: Working longer than the legal upper limit of 52 hours/week puts workers at a greater risk for depression. Females, low-income workers, and wage workers are more vulnerable to the negative consequences of long working hours on mental health.