Piecewise Growth Mixture Modeling of Adolescent Alcohol Use Data

This article addresses issues of heterogeneity in multiple-stage development as it corresponds to qualitatively different development in alcohol use during adolescence. Using a piecewise growth mixture modeling methodology proposed by Muthen (in press), a 2-piece linear growth model capturing growth trajectories in adolescent alcohol use during the transition from middle school (ages 11 to 13) to high school (ages 14 to 17; N = 81) was examined. It was hypothesized that 2 stages of alcohol use development with varying trajectories would exist in these data, the 1st corresponding to development during middle school (Growth Rate 1), followed by a 2nd stage of continuing growth during high school (Growth Rate 2). Results suggested the tenability of the 2-piece linear development in alcohol use and the emergence of 2 latent classes with individually varying transition points. Class 1 showed linear increases only during high school, whereas Class 2 showed a continued, linear growth throughout the middle and high school years. Findings suggest that the sample population under study is heterogeneous and consists of 2 subpopulations, each defined by its unique growth trajectories and individually varying transitional growth processes. The piecewise growth mixture modeling approach is likely to provide researchers with insightful information regarding qualitative differences in adolescent substance use development as well as a potentially useful modeling technique for intervention studies involving evaluation of program effectiveness.