Alcohol use typically begins during adolescence, with over 70% of US high school students (grades 9–12) reporting that they have consumed at least one drink, and over 20% reporting that they first drank alcohol by age 13 (Centers for Disease Control and Prevention, 2012). These early experiences with alcohol typically occur in social contexts (Ennett et al., 2006; Henry et al., 2005; Strycker et al., 2003). The influence of peers on one’s drinking behaviors has been widely studied. Two basic, complementary causal mechanisms (Caspi, 2002) have been proposed to explain the association between one’s own drinking and that of one’s peers: social selection and social influence. Individuals are capable of selecting peers based on their own drinking behaviors; they also might modify their own drinking behavior in response to peer influences (Bauman and Ennett, 1994; Cullum et al., 2012; Henry et al., 2005; Kiuru et al., 2010). The terms selection and influence have different denotations across studies. In this study, we will use them to refer to causal processes that are distinct from latent genetic and environmental correlations (Figure 1).
