Trajectories of Driving after Drinking among Marijuana-Using Youth in the Emergency Department: Substance Use, Mental Health, and Peer and Parental Influences

Background: The psychosocial correlates and longitudinal trajectories of driving after drinking (DAD) among youth remain understudied in at-risk populations. Objectives: We investigated the relationships of DAD trajectories and negative peer and parental influences, substance use, and mental health among predominantly marijuana-using youth seeking emergency department (ED) treatment. Methods: Data were from a 2-year prospective cohort study of drug-using patients (97.4% used marijuana) ages 14–24 seeking ED care for assault injury, or as part of a non-assaulted comparison group. Validated surveys measured DAD behaviors and correlates at baseline, 6, 12, 18, and 24 months. Latent class growth analysis identified characteristic DAD trajectory groups; baseline predictors were analyzed descriptively and using multinomial logistic regression. Results: Three DAD trajectory groups were identified among driving-age youth (n = 580): no DAD (NDAD; 55.2%), low-steady (LDAD; 29.0%), and high-declining (HDAD; 15.9%). In unadjusted analyses, HDAD youth were older, but otherwise similar to other groups demographically. Compared to NDAD, LDAD and HDAD group members had higher rates of drug and alcohol use disorders (p <.001). Further, HDAD group members had higher rates of anxiety symptoms and were more likely to be diagnosed with PTSD or depression than NDAD or LDAD youth (p <.05). Negative peer and parent influences were significantly higher in progressively more severe trajectory groups (p <.01). Adjusted effects from the multinomial model were analogous for peer and parental influences and substance use disorders, but not mental health. Conclusion: DAD is strongly associated with negative social influences and substance use disorders among marijuana-using youth, reinforcing their importance when developing interventions.