Amnesia is a partial or, in rare cases, a complete loss of memory. Everyone forgets minor daily incidents as time goes by, but a person with amnesia has large gaps in memory. People who suffer from amnesia lose the ability to recall past or recent experiences  They may even leave their homes, wander for a while, and start a new life somewhere else. This wandering while experiencing amnesia is called psychogenic fugue. 

Amnesia may be caused by emotional shock, senility, disease, physical injury or by a side effect of some drugs. In emotional shock, amnesia is usually restricted to events closely related to the cause of the shock. Doctors treat amnesia of emotional origin by hypnosis or with drugs. Diseases and physical injuries may cause actual changes in the brain, making recall impossible.