Because a prior report (Hamidovic et al., 2009) found amphetamines had differing effects on performance based on rs12364283 genotype, we conducted post-hoc analyses to examine whether differential risk is associated with this SNP based on amphetamine dependence status. We first confirmed that a higher prevalence of lifetime amphetamine dependence is found among heroin dependent cases [51.9% (N=697)] than controls [16.3% (N=66)]. We then observed significantly greater PTSD risk (Table 3) in those with one or more copy of the rs12364283 G allele who were also amphetamine dependent [OR 2.86 (1.92–4.27); p=2.6 × 10−7], than those who were either amphetamine dependent without a copy of the rs12364283 G allele or those with a copy of the rs12364283 G allele, but not amphetamine dependent (see Figure 1). Thus, in our sample, PTSD risk associated with rs12364283 occurs primarily among amphetamine dependent individuals. When these analyses were repeated in those individuals (N=1315) for whom BIS total score was available for inclusion as a covariate to control for self-reported impulsivity, results remained significant with risk only mildly reduced [OR 2.43 (1.56–3.81); p<.0001].
