If GABRA2 does confer risk for a broad spectrum of externalizing behaviors, it would be important to understand the mechanism(s) underlying these associations. Previous research suggests that behavioral disinhibition may be the heritable intermediate phenotype shared among externalizing problems [2] and, therefore, perhaps GABRA2 predicts externalizing problems through behavioral disinhibition. Complicating this proposition, however, are empirical observations that disinhibition is heterogeneous and consists of distinct facets [30]. To account for this heterogeneity, some studies examined associations between GABRA2 and distinct facets of disinhibition, finding that GABRA2 is related to adults’ NEO impulsivity (under negative affectivity) [23, 24], and to adolescents’ sensation seeking but not impulsivity [9]. One study also found that NEO impulsiveness partially mediated the effect of GABRA2 on adults’ lifetime alcohol problems [24].
