In a cohort of 14 refugees with PTSD and 15 without PTSD, we found significantly higher XRCC1 expression in PTSD patients than controls (U = 161.0, p = 0.009, Cohen’s r = 0.49), and positive correlations between the severity of PTSD symptoms and the expression of XRCC1 (rS = 0.57, p = 0.002) and PARP1 (rS = 0.43, p = 0.022). This evidence concerns the gene PARP1 and post-traumatic stress disorder.