Military experience and depression: a prospective multi-cohort analysis across nations

Depression is a growing public concern, but whether it is associated with military experience still needs investigation. This study aimed to examine this association among male veterans. We employed data from the Chinese Family Panel Study 2010-2020 (China), the Socio-Economic Panel 2009-2021 (Germany) and the Panel Study of Income Dynamics 2009-2021 (USA) and included 27300 male adults aged above 18 years. The Cox proportional hazards model was applied to examine the association between military experience and depression with subgroup analyses. The restrictive cubic spline model was used to estimate the nonlinear relationship. The mediating effect of chronic diseases on this association was also explored. In the USA and the pooled sample of Germany and the USA, the depression risk for those with military experience was increased by 88 % (1.88, 1.67-2.12) and 49 % (1.49, 1.34-1.66), respectively. It was reduced by 42 % (0.58, 0.42-0.79) in German veterans but not significantly different in Chinese veterans. Some age heterogeneity existed. In the USA and the pooled sample, no increased risk of depression was observed among older veterans, while in China, they faced a decreased risk (0.74, 0.55-0.99). There was a U-shaped relationship between military time and depression in Germany, the USA and their pooled sample. Chronic disease partially mediated the association between military experience and depression in Germany, the USA and their pooled sample. This study advocates for cross-national policy interventions providing tailored mental health support and chronic disease management to mitigate depression risks among military personnel, particularly new recruits and long-serving veterans.