NR3C1 and post-traumatic stress disorder: Other SNPs in genes involved in HPA axis regulation have also been found to be associated with PTSD, such as the CRHR1. Epigenome studies have found evidence of associations between levels of methylation in several genes with a regulatory role in HPA axis functioning—mainly NR3C1 and FKBP5—which can depend on the gene’s SNPs and on the gene’s location of methylation.