Our gene-environment interaction results conceptually map onto findings for a positive association between childhood trauma and cocaine addiction for those homozygous or heterozygous for the G (minor) allele at GABRA2 SNP rs11503014 (Enoch et al., 2010) in a clinically-ascertained African-American sample. However, in our Caucasian samples, the effects were with respect to the opposite allele (i.e., the association between life events and externalizing was more positive for those homozygous for the major allele at GABRA2 SNP rs279871 compared to those heterozygous or homozygous for the minor allele). We note that the effects in the present study are for the same genotype previously associated with alcohol dependence (Edenberg et al., 2004), conduct disorder (Dick, Bierut, et al., 2006), and, as previously found in the CDP sample, a greater likelihood of displaying an elevated-persistent trajectory of externalizing behavior in the context of low parental monitoring (Dick et al., 2009). Other studies report that the minor allele is the risk-increasing allele (Fehr et al., 2006); however, we note that inconsistency in the identity of the risk-increasing allele for GABRA2 may be attributable to
