With respect to longitudinal studies, affiliation with antisocial peers has often been examined in relation to mean externalizing trajectories (i.e., average baseline levels and rates of change), but rarely in relation to patterns of development observed within discrete subgroups of the broader population (i.e., via person-centered approaches). For example, Barnes and colleagues (2006) demonstrated that increases in baseline levels of peer’s antisocial behaviors among 506 adolescents (mean age 14.5 years) were linked with higher initial levels and rates of increase in adolescents’ alcohol misuse, illicit drug use, and delinquency across six annual assessments. In addition, Vitaro and colleagues (2005) showed that among adolescents reporting at least one friend, those whose peers collectively reported the most prominent increases in delinquency during the transition into adolescence also averaged the highest intercepts and rates of change in their own delinquent behavior across the early adolescent years.
