There has been a threefold increase in new cases of self reported post-traumatic stress disorder symptoms among combat-exposed military personnel since 2001, according to a new study. Concerns have been raised about the health impact of military deployment. Studies have estimated as many as 30% of Vietnam War veterans developed post-traumatic stress disorder at some point following the war and, among 1991 Gulf War veterans, as many as 10% were reported to have post-traumatic stress disorder symptoms years after returning from deployment.