A number of limitations must be considered when interpreting our findings. First, enthusiasm must be tempered until our results are replicated in an independent sample; doing so is particularly important given that the significance of the association with PTSD in the sample as a whole failed to meet the conservative Bonferroni correction for multiple testing. Our decision to apply this threshold rather other less conservative options may be viewed as overly stringent given that a number of the SNPs are in LD and thus are not entirely independent measures. Similarly, it is possible that by opting to include case status (i.e., heroin dependence) as a covariate in the genetic analyses, we may have underestimated the association for SNPs contributing to the shared genetic variance with PTSD. In addition, post-hoc analyses confirmed the lack of a significant association of rs12364283 with either heroin or amphetamine dependence. Separate analyses of case and control data found significant effects in both groups, demonstrating that our findings were not limited to heroin dependent cases. BIS data were not available on all participants and this could
