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 parental monitoring as a context that moderates the likelihood that individuals carrying the high-risk genotype at GABRA2 will display externalizing psychopathology. Thus, we theorize that parental monitoring acts as the moderator rather than the genotype acting as the moderator. We believe that in the case of GABRA2, parental monitoring, and the development of externalizing behavior, this represents the more plausible pathway of risk. In addition, we add a cautionary note that although we refer to the interaction as a gene-environment interaction, we cannot rule out the possibility that it represents an epistatic association (ie, gene-gene interaction). There was no association between GABRA2 and the measure of parental monitoring analyzed in our sample; however, it is possible that other genetic variants influence adolescents' behavior in a way that elicits differential parental monitoring, in which case the interaction could represent epistasis. However, even if this was the case, we still believe that mediation of the effect through the construct of parental monitoring
