Mental health problems as mediators between childhood trauma and cardiometabolic risk behaviours in the 2004 Pelotas Birth Cohort

Background Childhood trauma is associated with greater engagement in health risk behaviours (HRBs) that predispose to cardiometabolic disease. However, the mechanisms underlying these associations remain poorly understood. Mental health problems are hypothesised to mediate links between trauma and HRBs, but prospective evidence is limited, particularly among low‐ and middle‐income‐country youth. We examined whether mental health problems, specifically internalising and externalising problems, mediate longitudinal associations between trauma exposure and HRBs in a population‐based cohort of Brazilian youth. Methods We analysed data from the 2004 Pelotas Birth Cohort ( N  = 4,229). Cumulative trauma exposure was derived from repeated caregiver reports up to age 11. Internalising and externalising problems were assessed using the Strengths and Difficulties Questionnaire at age 15. HRBs were assessed at age 18, comprising smoking, alcohol and illicit drug use, ultra‐processed food intake and accelerometer‐measured physical (in)activity. We performed counterfactual mediation to estimate indirect effects from trauma to HRBs via internalising and externalising problems, both jointly and separately. Results There was a combined indirect effect of trauma on smoking and illicit drug use via internalising and externalising problems modelled simultaneously. When examined separately, externalising problems mediated the effect of childhood trauma on increased substance use (aORs = 1.02–1.03) and ultraprocessed food intake ( β  = 0.12) and, unexpectedly, higher physical activity ( β s = 0.10–0.30). No indirect effects via internalising problems were observed. Conclusions Our findings reveal the complex role of mental health in the trauma–cardiometabolic risk pathway among youth, with externalising problems increasing risk through substance use and poor diet, but also potentially mitigating the effects of trauma by reducing sedentary lifestyles. Further understanding of the emergence of risk behaviours for cardiometabolic disease in youth is critical to developing targeted prevention strategies.