COMT and post-traumatic stress disorder: The distributions of both COMT rs4680 (PTSD group: 31 Val/Val, 22 Met/Val, and 2 Met/Met; trauma-exposed control group: 88 Val/Val, 56 Met/Val, and 11 Met/Met) and BDNF rs6265 (PTSD group: 17 Val/Val, 27 Met/Val, and 11 Met/Met; control group: 38 Val/Val, 83 Met/Val, and 34 Met/Met) were in Hardy–Weinberg equilibrium (all P > 0.05).