Although the GABRA2–parental monitoring interaction described here is consistent with the mechanisms suggested by the moderation of latent genetic influences from the twin literature, it is notable that we conceptualize the relationship between this particular gene and environment differently from that reported for other specific gene-environment interactions in the literature. For example, with respect to the interaction between monoamine oxidase A and physical maltreatment in the development of antisocial behavior, the original report stated, “MAOA [monoamine oxidase A] was found to moderate the effect of maltreatment.”12(p851) Similarly, the original description of interaction between life stress and the serotonin transporter (5-HTT) gene on depression was titled, “Influence of Life Stress on Depression: Moderation by a Polymorphism in the 5-HTT Gene.”11 Thus, in both of these cases, the genotype was characterized as the moderator of an association between an environmental risk factor and behavioral outcome. In principle, gene-environment interaction can be conceptualized either as genetic moderation of environmental effects or environmental moderation of genetic effects.58 In the case of the interaction between GABRA2, parental monitoring, and externalizing behavior reported here, we conceptualize
