To summarize, we find evidence in an early adolescent population age approximately 11–14 (grades 6–8) for both selection of friends on the basis of the same alcohol onset status, and an increased risk of onset for youth with a higher proportion of friends with previous onset. These findings clarify the roles of selection and exposure in the earliest years of adolescence in terms of onset to first alcohol use, showing a positive selection-and-influence feedback process that explains how drinking diffuses through this population over time based on friendship linkages. Additionally, rate of onset increases from grade 6 to 8, and it is larger for youth who spend more unsupervised time with peers. Rate did not vary by gender, however, and the selection and exposure effects were not moderated by grade, adult supervision, or gender with either selection or exposure.
