Marijuana use trajectories among drug-using youth presenting to an urban emergency department: Violence and social influences

•Five marijuana use trajectory groups were identified among drug-using youth.•Aggression and male gender were baseline markers of more severe use trajectories.•Peer influences distinguished marijuana use trajectories over time.

AimsThis paper examined longitudinal marijuana use trajectories among drug-using youth presenting to the ED to inform intervention development.MethodsGiven interest in substance use and violence, this study oversampled those presenting with assault injuries. Assault-injured youth (ages 14–24) endorsing past 6-month drug use (n = 349), and a sex and age proportionally-sampled comparison group (n = 250) endorsing drug use, completed a baseline assessment and follow-ups at 6, 12, 18, and 24 months. Latent class trajectory analyses examined days of marijuana use over 2 years. Multinomial regression analyses examined baseline, 12-month and 24-month factors associated with substance use trajectory groups.ResultsTrajectory analyses identified 5 groups: Low (Low; 28.2%; n = 169); Intermittent (INT; 16.2%; n = 97); Moderate Decline (MD; 12.0%; n = 72); High decline (HD, 13.2%; n = 79) and Chronic (C; 30.4%; n = 182). At baseline, as compared to the Low group, the other trajectory groups were more likely to be male and have greater levels of physical aggression. At 12- and 24-months, negative and positive peer influences, incarceration and community violence were additional characteristics associated with the greater marijuana use trajectories (as compared to the Low group).ConclusionsInterventions for drug-using youth presenting to the urban ED should address peer influences, physical aggression and community violence exposure, given the association between these characteristics and greater marijuana use trajectories.