Higher XRCC1 (F = 2.39, p = 0.010, η2p = 0.10) and PARP1 (F = 2.15, p = 0.022, η2p = 0.09) expression accounted for slower repair of experimentally X-ray irradiation-induced DNA damage, highlighting the possible physiological relevance of altered DNA-repair gene expression in PTSD. The gene discussed is XRCC1; the disease is post-traumatic stress disorder.