 ObjectiveHypothesis: The objective of this application is to investigated the relationship between SLC6A3SLC6A4 and the mental health of veterans exposed to high levels of combat stress, specifically focusing on PTSD symptoms, related comorbidities, and treatment outcome. The central hypothesis is that specific genetic variants that adversely affect serotonin and dopamine neurotransmission constitute a risk for the emergence of PTSD and related comorbid symptoms after trauma exposure; and, some of these variants may further influence PTSD and related response. 