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

: The psychosocial correlates and longitudinal trajectories of driving after drinking (DAD) among youth remain understudied in at-risk populations. : 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. : 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. : Three DAD trajectory groups were identified among driving-age youth ( = 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 ( < .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 ( < .05). Negative peer and parent influences were significantly higher in progressively more severe trajectory groups ( < .01). Adjusted effects from the multinomial model were analogous for peer and parental influences and substance use disorders, but not mental health. : DAD is strongly associated with negative social influences and substance use disorders among marijuana-using youth, reinforcing their importance when developing interventions.