http://www.nimh.nih.gov/HealthInformation/ptsdmenu.cfm
National Institute of Mental Health, National Institutes of Health
Post-Traumatic Stress Disorder, PTSD, is an anxiety disorder that can develop after exposure to a terrifying event or ordeal in which grave physical harm occurred or was threatened. Traumatic events that may trigger PTSD include violent personal assaults, natural or human-caused disasters, accidents, or military combat.