Predictors of Off-Diagonal Binge Drinking and Marijuana Use Trajectory Groups Through the Transition to Adulthood.

Abstract

Binge drinking and marijuana use are serious health risk behaviors. Early onset, chronic users tend to receive the majority of clinical and empirical attention. However, developmental studies have identified multiple substance use trajectories through the transition to adulthood. Emerging from this work are two often overlooked subgroups of off-diagonal substance users who do not follow expected patterns of risk: 1) a late-onset group with low levels of use during adolescence but increasing use through the transition to adulthood; and 2) resilient youth with a family history of substance use disorder (FH+) but low substance use through the transition to adulthood. Using a developmental psychopathology perspective, this dissertation examined psychosocial, contextual, and neural predictors of off-diagonal substance use groups using a multi-level approach. A key finding from Chapter Two, which used national longitudinal samples from the Monitoring the Future (MTF) survey, was that late-onset youth were nearly indistinguishable from chronic high users on predictors in young adulthood, providing support for equifinality. Using data from the Michigan Longitudinal Study (MLS), a longitudinal community sample consisting predominately of families at high risk for substance use disorders, Chapter Three showed that late-adolescent reactive control and externalizing behaviors were significant predictors of resilience among FH+ youth. Chapter Four focused on the MLS subsample that completed functional magnetic resonance imaging (fMRI) assessments. Differences in neural functioning related to dual-systems models of risk-taking—inhibitory control and reward responsivity measured by a Go/No-Go task and the Monetary Incentive Delay Task, respectively—were found between resilient and heavy substance using FH+ youth. In addition, greater activation in the dorsolateral prefrontal cortex predicted substance use resilience versus risk among FH+ youth over and above psychosocial measures of reactive control and externalizing behaviors. By including longitudinal studies with breadth (MTF) and depth (MLS), this dissertation identified multidimensional developmental mechanisms associated with off-diagonal substance use. Findings contribute to existing literature and offer important theoretical and clinical implications.