Subsequent analyses examined the association between CHRM2 and trajectories of externalizing behavior (extended to a three-class solution with the incorporation of a nonlinear growth term) and tested for moderation by peer antisocial behavior (Latendresse et al., 2010). We found that, relative to the normative lower-risk externalizing trajectory, the likelihood of membership in the two higher risk trajectories increased with each additional copy of the risk allele at CHRM2. This association was exacerbated among those exposed to higher levels of peer group antisocial behavior. Accordingly, our findings were consistent with the evidence of moderation from twin studies, in which heritable influences were found to be higher under conditions of lower parental monitoring and higher peer deviance.
