In addition, Dick and colleagues have attempted to bridge the gap between the latent gene–environment interaction literature and specific measured gene–environment interactions by developing hypotheses about the risk associated with genes. On the basis of twin studies suggesting that genetic influences on adolescent substance use are moderated by parental monitoring (Dick et al. 2007b) and peer substance use (Dick et al. 2007a), the researchers tested for moderation of the association of two genes associated with adult alcohol dependence in the Collaborative Studies on Genetics of Alcoholism project. The two genes were for the γ-aminobutyric acid receptor (GABAR) subunit α-2 (GABRA2) (Edenberg et al. 2004) and the cholinergic muscarinic 2 receptor (CHRM2) (Wang et al. 2004). The researchers found evidence for gene-by-interaction effects in the direction predicted by the twin studies, namely genetic effects were enhanced under conditions of lower parental monitoring (Dick et al. 2009b) and higher peer-group antisocial behavior (Latendresse et al. 2011).
