Post Traumatic Stress Disorder (PTSD) is defined as a "complex anxiety disorder that may occur when individuals experience or witness an event perceived as a threat and in which they experience fear, terror, or helplessness." PTSD is sometimes summarized as “a normal reaction to abnormal events.” It was first defined as a distinctive disorder in 1980 and was originally diagnosed in veterans of the Vietnam War.
Although the veteran population is most heavily affected by PTSD, "it is now recognized in civilian survivors of rape or other criminal assaults; natural disasters; plane crashes, train collisions, or industrial explosions; acts of terrorism; child abuse; or war." (Gale Encyclopedia of Mental Health, 3rd ed.)
PTSD can affect almost anyone in any age group if they experience a traumatic event or series of events. National Institute of Mental Health studies showed that in 2007: