Young adult polysubstance use trajectories and later non-prescribed opioid use and drug use disorder symptoms: A propensity score-matched analysis.

Background: Longitudinal patterns of common substance use in young adulthood may identify risk for later opioid-related and other drug-related harm. We examined whether longitudinal trajectories of alcohol, cannabis, and nicotine use during young adulthood were associated with non-prescribed opioid use and other drug use disorder (ODUD) symptoms in adulthood. Methods: We analyzed restricted longitudinal Monitoring the Future panel data from 26 baseline cohorts (1976-2002). Group-based trajectory modeling identified polysubstance use trajectories from baseline through the first three biennial follow-ups. Trajectories were classified as low-use or high-use. Outcomes were any non-prescribed opioid use and ODUD symptoms between ages 35 and 55. Propensity score weighting estimated associations under average treatment effect for the treated, average treatment effect for the untreated, and average treatment effect estimands. Results: Five trajectory groups were identified and classified as low-use or high-use. The low-use trajectory included 14.7% of participants and was characterized by no cannabis or nicotine use and low-to-moderate alcohol use; the remaining trajectories involved high use of at least one substance. In average treatment effect models, high-use trajectory membership was associated with higher odds of later non-prescribed opioid use (OR=3.61; 95% CI: 3.34, 3.91) and ODUD symptoms (OR=15.9; 95% CI: 13.5, 18.8). Conclusion: In this US national longitudinal cohort, young adults with sustained high use of alcohol, cannabis, and/or nicotine had higher odds of non-prescribed opioid use and ODUD symptoms later in adulthood. These findings support targeted prevention, harm reduction, and cessation efforts addressing polysubstance use among young adults.