Consistent with prior evidence of allelic heterogeneity in ANK3 (Schulze et al., 2009), association was observed in two distinct regions—one more closely associated with externalizing, in the region just upstream and leading into the 3′ UTR, and a neighboring region more closely associated with PTSD. Even though these associations appear to be either PTSD- or externalizing-specific, apart from rs9804190, we caution against over-interpreting the specificity of association given our modest sample size. The observed β and OR were congruent for all associated SNPs (Table 1), with the minor alleles of each SNP having the same direction of effect for lower externalizing and lower risk of PTSD. Further, an analysis of association between externalizing and a core PTSD-associated haplotype was nominally significant. Moreover, while we have only identified associated SNPs in the 3′ region, further investigation of association of PTSD and externalizing to the 5′ region previously implicated in bipolar disorder and schizophrenia is necessary, since SNPs in this region may well demonstrate association in a larger sample. We can only conclude that the observed associations are consistent with allelic heterogeneity—although
