Association Between Diet and Mental Health Outcomes in a Sample of 13,887 Adolescents in Canada.

Introduction: The high prevalence of mental disorders among adolescents calls for community-based and population-level prevention strategies. Diet is an important intervention target for primary prevention of mental disorders among adolescents. We used data from a large longitudinal study of Canadian adolescents (aged 14-18 y) to examine prospective associations between diet and mental health outcomes. Methods: We estimated the effect of diet (ie, consumption of vegetables and fruit and sugar-sweetened beverages [SSBs]) at baseline on depressive symptoms, anxiety symptoms, and psychological well-being (measured by the Center for Epidemiologic Studies Depression Scale-Revised, Generalized Anxiety Disorder 7 scale, and Flourishing Scale, respectively) and at 1-year follow-up in a sample of 13,887 Canadian secondary school students who participated in the 2017-2018 and 2018-2019 cycles of the Cannabis, Obesity, Mental health, Physical activity, Alcohol, Smoking, and Sedentary (COMPASS) behavior study. We applied linear mixed-effects methods informed by a directed acyclic graph. Sensitivity analyses assessed the robustness of the effect estimates to unmeasured confounding variables. Results: Baseline SSB consumption was associated with greater severity of depressive (β = 0.04; 95% CI, 0.01-0.06) and anxiety (β = 0.02; 95% CI, 0-0.05) symptoms, particularly among male students, and poorer psychological well-being (β = -0.03; 95% CI, -0.05 to -0.01) at follow-up. Baseline vegetables and fruit consumption was positively associated with psychological well-being (β = 0.06; 95% CI, 0.03-0.10) but not other mental health outcomes at follow-up. Conclusion: Our results support the notion that diet should be part of comprehensive mental health prevention and promotion interventions to reduce the prevalence of mental health disorders among adolescents.