Substance Use Trajectories From Early Adolescence to Emerging Adulthood: A Comparison of Smoking, Binge Drinking, and Marijuana Use

Summary

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Over the past several years, there has been growing interest in identifying distinct developmental trajectories of substance use. Using data from the RAND Adolescent/ Young Adult Panel Study (N = 6,527), we synthesize our prior findings on patterns of smoking, binge drinking, and marijuana use from early adolescence (age 13) to emerging adulthood (age 23). We also present new data on how these trajectory classes compare on key psychosocial and behavioral outcomes during emerging adulthood. For each type of substance use, we found two periods of vulnerability: early adolescence and the transition to emerging adulthood. As expected, early users were at relatively high risk for poor outcomes at age 23 compared to consistent low-level users and abstainers, even if they reduced their use during adolescence. However, youths who were not early users, but steadily increased their use over time, also tended to be at relatively high risk. Results suggest that multiple prevention approaches might be needed to successfully reach at-risk youths.

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Substance Use Trajectories From Early Adolescence to Emerging Adulthood: A Comparison of Smoking, Binge Drinking, and Marijuana Use

INTRODUCTION

Recent statistics demonstrate the continuing widespread use of cigarettes, alcohol, and marijuana by individuals on the cusp of young adulthood (Johnston, O'Malley, & Bachman, 2003). For each of these substances, use typically begins in adolescence and steadily increases over time, reaching its highest peak during the period of emerging adulthood (Chen & Kandel, 1995). However, not all individuals follow this general pattern. Some youths increase their substance use during adolescence, whereas escalation does not occur for others until the college years. Some youths never progress from experimentation to regular use, and others are able to quit altogether. Focusing on these varied developmental trajectories of substance use may help identify specific periods during which prevention programs may be optimally effective, as well as identifying subgroups that may be of particular interest to researchers or practitioners (e.g., substance users who experience difficulties during the transitional period from adolescence to young adulthood). By creating more homogeneous subgroups of substance users, it may also provide increased precision in predicting behavior and outcomes (Rapkin & Dumont, 2000).

DEVELOPMENTAL TRAJECTORIES OF SUBSTANCE USE

Analytic techniques for identifying distinct developmental trajectories within a heterogeneous sample have evolved considerably over the past decade. Traditional latent growth modeling allowed for the identification of a single growth trajectory only, with variance in growth factors representing individual differences in growth (Duncan, Duncan, Stryker, Li, & Alpert, 1999). Semiparametric group-based modeling (Nagin, 1999), or latent class growth analysis, extended this framework by combining it with latent class analysis. This approach expresses individual differences in growth through the estimation of multiple discrete classes with distinct growth parameters, but is limited in that it assumes that the individuals in a class all have the same development. Latent growth mixture modeling (Muthén, 200 Ia, 200Ib; Muthén & Shedden, 1999) is the most versatile approach to studying trajectories of growth. It allows for individual variation within multiple discrete development...

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