Trajectories of alcohol, marijuana, and illicit drug use in a diverse sample of young men who have sex with men.

Introduction: Cross-sectional research has found that young men who have sex with men (YMSM) are more likely to engage in heavy drinking and to have higher rates of marijuana and other illicit drug use compared to their heterosexual peers, but considerably less is known about their patterns of substance use over time.

Methods: In this study, we combined two longitudinal samples of racially diverse YMSM (N=552) and modeled their substance use trajectories from late-adolescence to young adulthood, including their frequency of alcohol use, frequency of marijuana use, and poly-drug use, using piecewise latent curve growth modeling to model change from ages 17-21 and change from ages 22-24.

Results: We found that all three substance use behaviors increased linearly over the adolescent-to-adult transition. The trajectories for all three substance use behaviors were significantly correlated from ages 17-21. Black YMSM had significantly lower growth from ages 17-21 in alcohol, marijuana, and poly-drug use compared to White YMSM. Hispanic/Latino YMSM had significantly higher growth from ages 22-24 in alcohol use but significantly lower growth in poly-drug use compared to White YMSM. YMSM with higher alcohol frequency slopes and YMSM with higher marijuana use slopes were more likely to have alcohol-related and marijuana-related problems, respectively, at the last wave of the study.

Conclusions: The results of the present study suggest that the transition from adolescence to adulthood for YMSM is a time of increasing and co-varying substance use and may be a critical period for substance use behaviors to grow into substance use problems.