The development of alcohol use and outcome expectancies among American Indian young adults: a growth mixture model.

Adolescence is an important developmental period for understanding alcohol use. American Indian youth are a group for whom various preventive interventions focusing on alcohol use have been implemented but have not necessarily been widely successful, highlighting the need to further refine our approaches. In the work reported here, we followed 464 14- to 18-year-old American Indian youth annually for seven years. We examined the development of alcohol use and positive alcohol outcome expectancies in parallel, using growth mixture modeling to identify classes with different trajectories of alcohol use and expectancies. We found five classes; the largest (n = 198) was made up of youth who experienced increases in both alcohol use and positive outcome expectancies. Initial levels of outcome expectancies were related to subsequent changes in alcohol use, while the reverse was not true, suggesting that interventions focusing on outcome expectancies are appropriate for a substantial number of youth. However, class heterogeneity in the relationships between the two processes pointed out that changes in expectancies may not always precede changes in alcohol use. Thus, intervention design implications are discussed for the class structures.