Evidence of social influence has been reported among longitudinal studies of college students (Cullum et al., 2012) and adolescents (Urberg et al., 1997; Wills and Cleary, 1999). Others have reported reciprocal effects between one’s own drinking and that of one’s peers. Two longitudinal studies of Finnish adolescents found evidence of both selection and influence (Kiuru et al., 2010; Mercken et al., 2012). In community-based samples of US adolescents followed longitudinally, initial levels of peer alcohol use were predictive of later adolescent alcohol use and vice versa (Curran et al., 1997; Simons-Morton and Chen, 2006; Stappenbeck et al., 2010). Still other research suggests that, when controlling for social selection, social influence is largely inconsequential (Mundt et al., 2012). Not all studies explicitly model both selection and influence (e.g., (Cullum et al., 2012), and interpretation of results is complicated if selection is not controlled for when examining influence (Bauman and Ennett, 1994; Bauman and Ennett, 1996; Jaccard et al., 2005; Madden et al., 2002; Urberg et al., 1997).
