The psychological costs of war: military combat and mental health.

We exploit plausibly exogenous variation in overseas deployment assignment to estimate the effect of combat exposure on psychological well-being. Controlling for pre-deployment mental health, we find that active-duty soldiers deployed to combat zones are more likely to suffer from post-traumatic stress disorder (PTSD) than their counterparts deployed outside the United States in non-combat zones. Among those deployed to combat zones, those deployed to locales where they engage in enemy firefight or witness allied or civilian deaths are at an increased risk for suicidal ideation and PTSD relative to their active-duty counterparts deployed to combat zones without enemy firefight.