To test our assumptions we evaluated MECP2 mRNA levels in the blood of 132 male and female participants who were trauma-exposed with or without ensuing symptoms of PTSD in adulthood (PTSD and trauma controls, TC) or non-exposed throughout their lifetime (non-traumatized controls, NTC), and assessed whether MECP2 expression varied as a function of sex, ACE and trauma exposure. This evidence concerns the gene MECP2 and post-traumatic stress disorder.