Perhaps the clearest example of this comes from analyses of GABRA2. GABRA2 codes for the receptor for the central nervous system inhibitory neurotransmitter GABAA alpha-2 subunit. GABAA receptors are involved in the mesolimbic dopamine system (Enoch, 2008), suggesting that GABRA2 is likely involved in a range of reward-related disinhibited behaviors that broadly reflect the inability to control one’s impulses. GABRA2 was initially associated with adult alcohol dependence in multiple independent samples (Covault et al., 2004; Edenberg et al., 2004; Enoch et al., 2009; Zintzaras, 2012), and has also shown association with drug dependence (Agrawal et al., 2006). Analyses of 860 children and adolescents ascertained as part of the COGA study found association for GABRA2 SNP rs279871 with childhood conduct disorder symptoms (Dick et al., 2006). It was also associated with trajectories of behavior problems in the independent Child Development Sample (Dick et al., 2009). Another GABRA2 SNP (rs9291283) was also associated with conduct disorder symptoms in participants from the Genetics of Antisocial Drug Dependence sample (Melroy et al., 2014). Of note, rs279871 and rs9291283 are in linkage equilibrium (r2 =
