Relationships among working hours, job stress, psychological capital, and depressive symptoms among Chinese medical staff: a moderated mediation model

Background Although several studies have revealed an association between long working hours and depressive symptoms, the mechanisms underlying this association are not entirely clear. This study examined the complex interplay among working hours, job stress, psychological capital, and depressive symptoms among Chinese medical staff via a moderated mediation model. Methods Utilizing data from the National Occupational Health Risk Assessment on Long Working Hours program (2021–2023), this cross-sectional study focused on medical staff, including both doctors and nurses, from tertiary Grade A hospitals. Web-based questionnaires were employed to measure variables using the Patient Health Questionnaire-9, Core Occupational Stress Scale, and 24-item Psychological Capital Questionnaire. Data analyses were conducted via SPSS 26.0 and Hayes’ PROCESS macro (Model 4 for mediation; Model 59 for moderated mediation) with 5,000 bootstrap samples to assess direct/indirect effects between working hours, job stress, psychological capital, and depressive symptoms. Results A total of 4,576 participants from 20 tertiary hospitals with valid questionnaires were included. The prevalence of depressive symptoms was 33.9%. Working hours (r = 0.276, p < 0.001) and job stress (r = 0.175, p < 0.001) were positively correlated with depressive symptoms, whereas psychological capital was negatively correlated with both job stress (r = -0.319, p < 0.001) and depressive symptoms (r = -0.439, P < 0.001). The findings indicate that job stress has an indirect-only mediating effect on the relationship between working hours and depressive symptoms. Additionally, PsyCap moderates the indirect pathway between working hours and depressive symptoms via job stress. Specifically, higher levels of psychological capital weaken the impact of job stress on depressive symptoms. Conclusion Working hours are positively associated with depressive symptoms among Chinese medical staff, with job stress mediating and psychological capital moderating this association. Therefore, addressing medical staff’s mental health requires effective workload management systems and resilience-building interventions aimed at improving psychological resources.