Caffeine Consumption and Adolescent Mental Health: The Role of Sleep and Brain Structure

BACKGROUND: Caffeine is a widely consumed psychoactive substance, with use beginning during adolescence, a sensitive period of neurodevelopment. Despite its widespread, unregulated use, links between caffeine consumption and adolescent brain structure and mental health remain poorly understood. METHODS: We examined the association between caffeine intake and brain structure in 9632 adolescents aged 9-11 years. Caffeine consumption (intake of coffee, tea and soft drinks) and mental health were assessed via self-report. Cortical thickness and surface area were derived from structural MRI scans. Linear mixed-effects models tested associations between caffeine intake and brain measures. Structural equation modeling was used to test whether sleep duration and brain structure mediated the association between caffeine intake and mental health outcomes assessed at the 6-month and 18-month follow-up. RESULTS: Higher total caffeine intake was associated with lower total cortical surface area (B=-0.03,SE=0.01,p=.001) and lower surface area in 22 regions across four lobes, driven largely by soft drink consumption, with some additional associations emerging for coffee and espresso intake with cortical thickness. All associations were evident at consumption levels as low as one cup per week. Shorter sleep duration and lower surface area sequentially mediated the association between higher caffeine intake and greater mental health problems in the future. CONCLUSION: Findings highlight the need for evidence-based guidelines on adolescent caffeine consumption to support neurodevelopment and mental health.