Background: Some patterns of cannabis use may presage risk for long-term negative effects. We examined associations between a novel adolescent cannabis misuse scale and early-adult life course outcomes.Methods: We performed a secondary data analysis of a cohort of Los Angeles, CA high school students from grade 9 through age 21. Participants reported baseline individual demographic and family characteristics at grade 9, adolescent cannabis misuse (8-items) and alcohol misuse (12-items) at grade 10, and outcomes at age 21. We used multivariable regression to model the associations of cannabis misuse scale score with problem substance use (defined as any of: 30day illegal drug use, 30-day use of another's prescription to get high, hazardous drinking) and several secondary outcomes (behavioral, mental health, academic, social determinants of health), adjusting for covariates. Parallel analyses were conducted for alcohol misuse.Results: The 1,148 participants (86% retention) were 47% male, 90% Latinx, 87% US born, and 40% native English speakers. Approximately 11.4% and 15.9% of participants reported at least one item on the cannabis and alcohol misuse scales, respectively. At age 21, approximately 6.7% of participants reported problem substance use, which was associated with both Cannabis and Alcohol Misuse Scales (OR 1.31, 95%CI[1.16, 1.49] and OR 1.33, 95%CI[1.18, 1.49], respectively). Both scales were similarly associated with outcomes in all four categories. Conclusions: The Adolescent Cannabis Misuse Scale is a promising tool for identifying early patterns of substance use that predict future negative outcomes and enabling early intervention at a critical period in youth development.