Predicting post-traumatic stress disorder in veterans: Interaction oftraumatic load with COMT gene variation

Background: Because post-traumatic stress disorder (PTSD) by definition can occur only after exposure to a traumatic event, military veterans who are at high risk for trauma exposure are a particularly relevant population for studying the interaction of trauma with genetic factors that may predispose for the disorder. A number of studies have implicated specific genes as possible risk factors in developing PTSD, including the catechol-O-methyltransferase gene ( COMT). Methods: Data from Iraq War veterans ( n=236) were used to examine the interaction between COMT and traumatic experiences in predicting later development of PTSD symptoms. Subjects were assessed for exposure to traumatic events both before and during deployment. Results: The interaction between trauma load and COMT was a significant predictor of PTSD symptoms. Those with the heterozygous genotype (Val/Met) showed fewer symptoms associated with trauma exposure compared to those with either homozygous genotype. This interaction remained significant after controlling for other risk factors for PTSD, including personality dimensions of Internalizing and Externalizing. Conclusions: COMT genotype affects risk for development of PTSD symptoms following exposure to trauma.