Trajectories of polysubstance use: Are past-year internalizing and externalizing problems associated with trajectories of polysubstance use over time?

Prevention efforts should consider internalizing problems and associated trajectories of high-risk polysubstance use (e.g., cigarette-leading and cigarette-cannabis co-leading) as well as externalizing problems and associated trajectories of high-risk polysubstance use (e.g., cannabis-leading), when designing interventions to prevent polysubstance use.