gene and behavior problems would be moderated by parental monitoring, based on our work in the Finnish twin studies showing that parental monitoring moderates the importance of genetic effects (Dick et al., 2007b). These hypotheses were supported: GABRA2 was associated with trajectories of externalizing behavior across adolescence, with the genotype previously associated with adult alcohol dependence in COGA associated with persistent, elevated levels of behavior problems across adolescence in CDP. Furthermore, this association was moderated by parental monitoring: the association between the genotype and behavior problems was stronger under conditions of lower parental monitoring, attenuated under higher parental monitoring (Dick et al., 2009). A second set of analyses produced similarly exciting results in the sample. CHRM2 is another gene associated with alcohol dependence in the COGA project (Wang et al., 2004) and subsequently replicated in an independent sample (Luo et al., 2005), We genotyped markers across this gene in CDP, and, parallel to GABRA2, found associations with trajectories of externalizing behavior. Further, we tested whether this association was moderated by peer group antisocial behavior based on previous twin studies demonstrating that genetic influences on substance use and problem behavior are enhanced as individuals are exposed to higher levels of peer
