Are Substance Use Patterns Established in Adolescence? Examining Transitions in Substance Use from Adolescence to Young Adulthood

Introduction: Research on trajectories of substance use consistently report increases across adolescence, peaking in late adolescence/early young adulthood, and subsequently decline. However, these studies tell us little about differential patterns of adolescent substance use or transition between patterns over time. Responding to the heterogeneity in early patterns of substance use, past studies have leveraged person-centered approaches using various finite mixture models to identify substance use classes in adolescence. While these studies have identified differential substance use classes, transitions between classes across adolescence are not well understood. A better understanding of how high-risk adolescent use patterns become established is needed. The current study examined substance use classes during adolescence and young adulthood and subsequent transitions among classes. Method: Data were collected biennially from 662 youth across six measurement assessments. Latent Class Analysis was used to identify substance use classes at each of the six waves based on four types of substance use: cigarette, alcohol, marijuana, and illicit drug use. We then examined transition probabilities from early adolescence (12 – 18) to young adulthood (22 – 28) using Latent Transition Analysis (LTA). Results: Across all six waves, a three-class model fit the data best and included a poly-use class, that had high probabilities of use among all substances, a co-use class, that had high probabilities of use of alcohol and marijuana, and an alcohol-dominate class that started with low probabilities of use among all substances, with increasing probabilities of alcohol use over time. Using LTA, we examined transitions between classes across the six waves. The proportion of youth remaining in the same class was high between waves. Specifically, the probability of remaining in the poly-use class was the most stable from one wave to the next, followed by the alcohol-dominate class. The stability for the co-use class was more variable, with less stability during later adolescence. For individuals that transitioned between classes, very few transitioned from alcohol-dominate to poly-use and vice versa, with most functioning through co-use. The largest transitions occurred among the co-use class, with more individuals transitioning up to the poly-use class than down to the alcohol-dominate class. Conclusions: While lasting effects of early substance use patterns were found, for many, transitions between classes were also common with most transitioning to use more substances. Distinguishing stable from transitioning patterns of use provides an opportunity for prevention and intervention efforts to employ targeted strategies aimed at disrupting high-risk substance use patterns.