The role of parents and older siblings in predicting adolescent substance use: Modeling development via structural equation latent growth methodology.

Using latent growth curve methodology, this study investigated developmental trends in adolescent, parent, and older sibling substance use across a 3-year period and the predictive effect of these trends on adolescent substance use 2 years later. Participants were 101 adolescents (50 boys and 51 girls) who were an average of 12.34 years old at the first assessment, their parents, and an older sibling. Results indicate that although both parents and siblings contribute to the level of adolescent use, only siblings appear to contribute to the adolescents' subsequent substance use development. The adolescents' developmental trajectory was the best predictor of later use, but siblings contributed to later use indirectly through their influence on adolescents' substance use development. Findings discuss the role of sibling and parent substance use on adolescent substance use and emphasize the utility of latent growth modeling in the study of developmental change.