Abstract
PURPOSE: Both substance use and depression are common in adolescence and often comorbid. Past research has produced conflicting results on whether there is a temporal relationship, and if so, in which direction it operates and how it may vary by sex. We examined the longitudinal associations between substance use frequency and depressive symptoms from adolescence into young adulthood and whether the associations were moderated by sex. METHODS: With data from Waves I, III, and IV of the National Longitudinal Study of Adolescent to Adult Health (n = 9,816), we used growth curve models to test if depressive symptoms predicted marijuana use or binge drinking frequency (Self-Medication Model) or if substance use frequency predicted depressive symptoms (Stress Model). Moderation by sex and age was tested for both potential pathways. RESULTS: Increases in adolescent depressive symptoms, compared to no symptoms, were associated with a steeper predicted increase in marijuana use frequency from adolescence to young adulthood. Increases in persistent binge drinking or marijuana use frequency had concurrent positive associations with depressive symptoms from adolescence to young adulthood, and these associations were significantly stronger for females compared to males. CONCLUSIONS: The results not only support the Self-Medication Model for marijuana use but also provide modest support for the Stress Model, that substance use is associated with depressive symptoms, especially for females.