It is possible that impulsiveness and alcohol involvement may share a common underlying biological pathway such that particular genetic variants are associated with increased risk for alcohol involvement and that this effect is mediated by impulsiveness. The identification of the genetic risk for both impulsive behavior and alcohol involvement may help to identify the biological mechanisms underlying these complex traits. We previously reported (Villafuerte et al., 2012) an association between GABRA2 and impulsiveness in a sample enriched for alcoholism. Gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the CNS, has a role in risk for developing alcohol use disorder (AUD) through the fast-acting receptor complex, GABAA (Krystal et al., 2006, Grobin et al., 1998). Repeated alcohol exposure affects the GABA system (Grobin et al., 1998) through binding sites at the GABA receptors, reducing neural inhibitory action. Genetic variation in GABRA2 has been reproducibly associated with both alcoholism (Agrawal et al., 2006, Bauer et al., 2007, Covault et al., 2004, Edenberg et al., 2004, Enoch et al., 2006, Fehr et al., 2006, Lappalainen et al., 2005, Lind et al., 2008a, Lind et
