to moderate the overall importance of genetic influences on that outcome. This is the strategy we have used to further characterize the risk related to genes associated with alcohol dependence in the Collaborative Study on the Genetics of Alcoholism. On the basis of our twin studies suggesting that genetic influences on adolescent substance use are moderated by parental monitoring (Dick et al. 2007c) and peer substance use (Dick et al. 2007a), we tested for moderation of the association of GABRA2 (Edenberg et al. 2004) and CHRM2 (Wang et al. 2004) as a function of parental monitoring and peer group antisocial behavior, respectively. We found evidence for gene-environment interaction effects in the direction predicted by the twin studies, namely, genetic effects were enhanced under conditions of lower parental monitoring (Dick et al. 2009) and higher peer group antisocial behavior (Latendresse et al. 2010).
