OXTR and post-traumatic stress disorder: This was also true for FKBP5, where we focused on 5 CpGs in intron 7, previously associated with PTSD risk following early life adversity38, and the OXTR gene, where we investigated 16 CpGs in a putative enhancer region—characterized by H3K27 acetylation peaks—in intron 3 of the gene.