Examining developmental trajectories in adolescent alcohol use using piecewise growth mixture modeling analysis

Objective: This study examined issues of heterogeneity in multiple stage de velopment as it corresponds to qualitatively different developmental trajec tories in alcohol use during adolescence. Method: Using a piecewise growth mixture modeling methodology a two-piece g rowth model capturing growth trajectories in adolescent alcohol use from mi ddle school (Grades 6 through 8) to high school (Grades 9 through 12) was e xamined (N = 179; 54% male). It was hypothesized that (1) two stages of alc ohol use development with varying trajectories would exist in these data (t he first corresponding to development during middle school, followed by a s econd stage of continuing growth during high school) and (2) there would be multiple growth trajectories (subgroups) of alcohol use in the stage-wise development, with varying effects in initial alcohol use and growth rates o f alcohol use. Results: Results indicated the tenability of the two-piece growth model of alcohol use with heterogeneity in the population comprising two distinct la tent developmental trajectory classes. Class 1, with a high initial status of alcohol use at Grade 6, showed an upward increase in trajectory only dur ing high school. Class 2, with a low initial status of alcohol use at Grade 6, showed a linear increase in middle school with a second growth spurt at high school entry and continuity in growth throughout the high school year s. Analyses, incorporating time-invariate covariates, indicated varying inf luences of gender, early levels of deviant behavior, family structure (sing le vs two parent), peer encouragement and parent disapproval of alcohol use , and adolescent deviant behavior upon high school entry, on the two trajec tory classes. Results also showed effects of the identified trajectories, w ith varying magnitudes, on later substance use in young adulthood with Clas s 1 showing the strongest continuity in later substance use. Conclusions: Findings suggest heterogenous development of alcohol use in th e adolescent population, associated with varying background and covariate i nfluences. In addition, this heterogeneity is linked to alcohol and other s ubstance use in young adulthood.