When we expanded our attention beyond rs9804190, analyses revealed four ANK3 SNPs associated with externalizing, the most significant of which was rs1049862 (p=0.00040). In addition, seven ANK3 SNPs in LD with rs9804190 were associated with PTSD at the p<0.01 level. The most significant of these was a cluster of three SNPs in complete LD. By examining patterns of LD between PTSD-associated SNPs, we identified a haplotype containing the high-expressing rs9801490 T allele that was more significantly associated with a protective effect for PTSD than any single SNP. This haplotype was also nominally associated with externalizing, again with a protective effect. Omitting those with either bipolar 1 or 2 from our analysis did not change our results, hence we do not believe that the presence or absence of bipolar disorder is central to the increased risk of PTSD or externalizing associated with ANK3 variants. It is more likely that ANK3 variants are not specific to any one disorder, as recent research has indicated that some of the common genetic risk variants (and one ANK3 variant in particular) may be shared across a broad class of psychological disorders (Cross-Disorder Group of the Psychiatric Genomics Consortium, 2013).
