Alcohol and marijuana use trajectories in a diverse longitudinal sample of adolescents: examining use patterns from age 11 to 17 years

Aims We tested race/ethnic differences in alcohol and marijuana (AM) trajectories (comprising an intercept term, reflecting overall probability of use, and a slope term, reflecting change in probability of use) during adolescence, whether AM use trajectories predicted high school outcomes, and whether outcomes differed by race/ethnicity after controlling for trajectory of AM use. Design This longitudinal study involved 6509 youth from 16 middle schools in Southern California surveyed from age 11.5 (2008) to age 17 (2015) years; all surveys assessed AM use, and the final survey also examined high school outcomes. Setting Youth completed five surveys in middle school and two on‐line surveys in high school. Participants The sample was 50% male and 80% non‐white. Measurements Intercept (at 2.75 years post‐baseline) and slope of AM use were examined as outcomes for race/ethnic differences. AM use trajectories were examined as predictors of academic performance and unpreparedness, social functioning, mental and physical health and delinquency. Findings We found differences in trajectories of use by race/ethnicity, with white youth reporting a higher overall intercept of alcohol use compared to all other groups (versus Asian P