An unusual form of motivated forgetting is called psychogenic amnesia in which a very severe emotional stressor causes one to lose a large amount of personal memories without an observable biological cause. Another reaction to a very severe stressor is called post traumatic stress disorder. People who have been subject to a traumatic event that has included death of others or a possibility of death or severe injury to oneself cannot forget these memories. This sometimes leads to flashbacks and nightmares that cause people to re-live these traumatic events for long periods afterwards.Canadian Mental Health Association. (2010) Post Traumatic Stress Disorder. Retrieved from http://www.cmha.ca/bins/content_page.asp?cid=3-94-97
