Adolescent Marijuana Use and Depressive Symptoms in Early Adulthood: A Longitudinal Analysis

Background Marijuana use is prevalent during adolescence and the transition to adulthood, but its association with subsequent depressive symptom severity remains uncertain.Objective To estimate the population-level difference in depressive symptom severity in early adulthood associated with marijuana use across adolescence and the transition to adulthood.Methods Data from the National Longitudinal Study of Adolescent to Adult Health were analyzed. Exposure was defined as any reported past-30-day marijuana use across Waves I–III, compared with no use at all three waves. Depressive symptoms at Wave IV were measured continuously using the Patient Health Questionnaire-8. Targeted maximum likelihood estimation with Super Learner was applied separately within 10 multiply imputed datasets to estimate the average treatment effect after adjustment for prespecified measured covariates. Estimates were pooled using Rubin’s rules.Results The analytic cohort included 3,488 participants, of whom 2,293 (66%) were classified as exposed and 1,195 (34%) as unexposed. Reported marijuana use across Waves I–III was associated with higher levels of depressive symptoms at Wave IV; the pooled difference was 0.92 points (95% CI: 0.12–1.72). Exploratory analyses indicated that depressive symptom levels and changes varied across marijuana use histories and did not follow a simple cumulative pattern.Conclusion Marijuana use during adolescence and the transition to adulthood was associated with higher depressive symptom severity in early adulthood. The estimate supports a long-term population-average association, and exploratory findings also suggest variation across marijuana use histories, although these patterns require further confirmation.