Adolescent substance use outcomes in the Raising Healthy Children project: a two-part latent growth curve analysis.

Raising Healthy Children (RHC) is a preventive intervention designed to promote positive youth development by targeting developmentally appropriate risk and protective factors. In this study, the authors tested the efficacy of the RHC intervention on reducing adolescent alcohol, marijuana, and cigarette use. Ten public schools, which comprised 959 1st- and 2nd-grade students (54% male students, 18% minority, 28% low socioeconomic status), were matched and assigned randomly to either intervention or control conditions. A 2-part latent growth modeling strategy was used to examine change in both use-versus-nonuse and frequency-of-use outcomes while students were in Grades 6-10. Results indicated significant (p < .05) intervention effects in growth trajectories for frequency of alcohol and marijuana use but not for use versus nonuse. These findings provide support for preventive interventions that take a social development perspective in targeting empirically supported risk and protective factors and demonstrate the use of 2-part models in adolescent substance use research.