The Moderating Effect of Generation on the Association Between Long Working Hours and Mental Health: A Cross-Sectional Study of Korean Employees

<b>Background/Objectives:</b> Long working hours are a recognized risk factor for poor mental health, but their impact may vary across generations. Millennials and Generation Z (MZ generation) have received attention for their distinct values, work-life expectations, and communication styles compared with older cohorts. The present study assessed generational differences (MZ vs. non-MZ) in the association between weekly working hours and depressive and anxiety symptoms among Korean employees. <b>Methods:</b> We analyzed cross-sectional data from 11,372 employees (68.0% men; mean age = 36.7 years) who underwent mental health screenings between 2020 and 2022. Participants born on or after 1 January 1980, were classified as belonging to the MZ generation (<i>n</i> = 7538). Symptoms of depression and anxiety were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D) and the Clinically Useful Anxiety Outcome Scale (CUXOS). Multiple linear regression models tested the interaction between mean-centered weekly working hours and generation, adjusting for sociodemographic covariates. <b>Results:</b> Longer working hours were significantly associated with greater depressive (B = 0.080, <i>p</i> < 0.001) and anxiety (B = 0.119, <i>p</i> < 0.001) symptom severity. Significant interactions between generation and working hours were observed for both depression (B = 0.140, <i>p</i> < 0.001) and anxiety (B = 0.182, <i>p</i> < 0.001). Generation-stratified models showed that the increase in symptom severity per additional work hour was approximately three-fold higher in the MZ generation than in the non-MZ generation. <b>Conclusions:</b> The mental health burden of long working hours is amplified in the MZ generation. Generation-sensitive workplace health strategies are needed to address this vulnerability.