The associations that we observed between peer group antisocial behavior and developmental heterogeneity in externalizing behavior were in the expected direction, though they were not as significant as we might have expected. While the existing literature generally suggests a detrimental influence of deviant peers, these findings mostly derive from studies examining more temporally proximal indices of externalizing behavior. In the present study, we tested only prospective associations between indices of peer group antisocial behavior at age 12 and trajectories of externalizing behavior spanning adolescence and into young adulthood (ages 12–22). As such, it is not altogether surprising that exposure to antisocial peers as assessed in preadolescence would not have strong main effects on long-term externalizing behavior patterns. We believe this makes the fact that we find evidence for interactions between peer group antisocial behavior and genetic predispositions, as measured by SNPs within CHRM2, all the more striking. In addition, it is important to note that the rather modest association that we observe is not at odds with extant evidence supporting a more robust association between antisocial peers and externalizing behavior,
