We hypothesized that (1) symptomatic reduction of PTSD after placebo and MDMA-assisted therapy would be predicted by changes in DNA methylation on NR3C1, FKBP5, and CRHR1; and (2) MDMA-assisted therapy group would exhibit more methylation change compared to placebo, related to the additional efficacy conferred by MDMA relative to placebo conditions. This evidence concerns the gene CRHR1 and post-traumatic stress disorder.