Of the 51 CpG sites with prior reports of association with PTSD (Additional file 1: Table S5), only the AHRR locus reported by Smith et al. survived correction for multiple testing (padj = 0.00047), which was not surprising given the fact that cg05575921 was near genome-wide significant in our EWAS. Here, AHRR is linked to post-traumatic stress disorder.