All analyses were limited to trauma-exposed individuals (N=1749). The relationships between PTSD and control variables [i.e., case status (heroin dependence) and sex] and descriptive analyses characterizing separately by case status those with, and without, PTSD were performed using SAS 9.2. Association analyses with PTSD as the dependent variable, and including sex and heroin dependence case status as independent variables, were performed using logistic regression in PLINK (Purcell et al., 2007) to examine the log-additive effects of the minor allele dosage separately for each of the 1430 remaining SNPs. An adjusted significance threshold of 3.50 × 10−5 (i.e.,.05/1430 SNPs) was used for these association analyses; this value was obtained by applying a strict Bonferroni correction for multiple testing which assumes all SNPs are statistically independent measures. Dummy variables were coded to represent jointly lifetime amphetamine dependence (missing in one individual who was dropped from these analyses) and the presence of at least one rs12364283 G allele as follows: both amphetamine dependence and the rs12364283 G allele present; amphetamine dependence alone, and the rs12364283 G allele alone (those with neither amphetamine dependence
