This social network study investigated the moderating role of self-control in the association between friendship and the development of externalizing behavior: Antisocial behavior, alcohol use, tobacco use. Previous studies have shown inconsistent findings, and did not control for possible friendship network or selection effects. We tested two complementary hypotheses: (1) That early-adolescents with low self-control develop externalizing behavior regardless of their friends' behavior, or (2) as a result of being influenced by their friends' externalizing behavior to a greater extent. Hypotheses were investigated using data from the SNARE (Social Network Analysis of Risk behavior in Early adolescence) study (N = 1144, 50 % boys, M age 12.7, SD = 0.47). We controlled for selection effects and the network structure, using a data-analysis package called SIENA. The main findings indicate that personal low self-control and friends' externalizing behaviors both predict early adolescents' increasing externalizing behaviors, but they do so independently. Therefore, interventions should focus on all early adolescents' with a lower self-control, rather than focus on those adolescents with a lower self-control who also have friends who engage in externalizing behavior.
Keywords: Alcohol use; Antisocial behavior; SIENA; Self-control; Social network analysis; Tobacco use.