Post-Traumatic Stress Disorder is when a person experiences symptoms of anxiety due to a major stressful experience (the type of experience that would induce fear in most people). Examples include near death experiences such as major car or plane accidents, or being the victim of violence.
The person often experiences 'flash-backs' of the traumatic event, avoids situations that remind them of the traumatic event, and experiences other symptoms such as being on edge and difficulty sleeping.
Many people can’t remember some of the events surrounding the trauma.
American Psychiatric Association (1994). Diagnostic and Statistical Manual of Disorders (DSM-IV) Washington, American Psychiatric Association.
Christensen, H. and Griffiths, K. (2006). "MoodGYM Website" from http://moodgym.anu.edu.au/