Best friends and alcohol consumption in adolescence: a within-family analysis.

Although friends and siblings are considered to be important role models in adolescents' peer contexts, these peer influences on adolescent alcohol consumption over time are seldom examined simultaneously in a within-family design. The present study examined the relative impact of alcohol use of the best friend, adolescent sibling and sibling's best friend on the development of alcohol consumption during adolescence. Data reported in this study are part of an ongoing longitudinal questionnaire study among families with two adolescent siblings (N=416). Results from structural equation modeling showed a strong similarity in drinking between best friends and adolescents cross-sectionally. Over time, however, only marginal effects of friends alcohol use on drinking of the youngest sibling, and no effects for the oldest sibling were found. Robust evidence was found for peer-selection processes. In addition, we found a moderate to high relative similarity in drinking within sibling pairs, but no longitudinal effect of sibling's drinking. We also found no support for a possible additional influence of sibling's best friend's drinking on adolescent drinking. Therefore, we tested several potential moderating variables on peer influences, but found no effects of a set of relationship characteristics or individual characteristics on the links between peer and adolescent drinking over time.