"Posttraumatic stress disorder (commonly referred to by its acronym, PTSD) is a severe anxiety disorder that can develop after exposure to any event which results in psychological trauma.This event may involve the threat of death to oneself or to someone else, or to one's own or someone else's physical, sexual, or psychological integrity, overwhelming the individual's psychological defenses.

PTSD is a less frequent and more enduring consequence of psychological trauma than the more frequently seen acute stress response. PTSD has also been recognized in the past as railway spine, stress syndrome, shell shock, battle fatigue, traumatic war neurosis, or post-traumatic stress syndrome.

Diagnostic symptoms include re-experiencing original trauma(s), by means of flashbacks or nightmares; avoidance of stimuli associated with the trauma; and increased arousal, such as difficulty falling or staying asleep, anger, and hypervigilance. Formal diagnostic criteria (both DSM-IV and ICD-9) require that the symptoms last more than one month and cause significant impairment in social, occupational, or other important areas of functioning (e.g. problems with work and/or relationships)""(http://en.wikipedia.org/wiki/Posttraumatic_stress_disorder).