BDNF Val66Met polymorphism and posttraumatic stress symptoms in U.S. military veterans: Protective effect of physical exercise.

The Met allele of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism is associated with reduced levels of BDNF release, heightened hypothalamic-pituitary-adrenal axis reactivity, and impaired fear extinction. As a result, Met allele carriers may be at risk for greater severity of posttraumatic stress disorder (PTSD) symptoms. In this study, we examined the relationship between the BDNF Val66Met polymorphism and PTSD symptoms in two nationally representative samples of European American U.S. military veterans (main sample, n = 1386; replication sample, n = 509). Results revealed that, relative to Val/Val homozygotes, Met allele carriers reported greater severity of lifetime and current PTSD symptoms, specifically re-experiencing symptoms. Met allele carriers with high trauma burden also reported greater severity of lifetime and past-month PTSD symptoms. Greater engagement in physical exercise moderated this gene-by-environment interaction. Specifically, among veterans with high lifetime trauma burden, Met allele carriers who exercised had significantly lower severity of PTSD symptoms compared to those who did not exercise. These findings suggest that interventions designed to bolster engagement in physical exercise may help mitigate PTSD symptoms in veterans who are Met allele carriers and highly exposed to trauma.