Amnesia is a disturbance of the brain that causes the person to forget a period of his or her life. Despite being a popular plot in movies and novels, amnesia is quite rare in real life. There are two basic causes of amnesia: organic, where the brain is actually damaged, and functional, where the causes are psychological. Amnesia can happen to anybody, at any age.

The most common types of amnesia are:
• Traumatic amnesia is often temporary and happens after a head injury. The duration and intensity of the amnesia is related to the type of injury received, but memory often returns after the patient recovers.

• Dissociative amnesia is common in people who experience traumatic events such as rape. While the person can remember everything about her life, the specific traumatic event is blocked from memory. Childhood amnesia is closely related, and it involves the blockage of events from childhood, usually involving abuse or traumatic experiences.

• Global amnesia, the most total type of memory loss, often accompanies post-traumatic stress disorder. While memory usually doesn't completely returns, the patient can sometimes experience spontaneous flashes of memory, often of the traumatic events itself. Global amnesia is most often seen in elderly people.

• Some physiological disorders, such as long-term alcoholism, malnutrition, and Alzheimer's disease can also cause memory loss.

• Damage to the temporal lobes of the brain usually result in either anterograde amnesia, where new events cannot be remembered for more than a few minutes; or retrograde amnesia, where the person will not be able to remember anything before the accident but it's capable of creating new memories.

• One of the most common types of amnesia is source amnesia, in which a person remembers information but is unable to explain how or when he obtained it.

The most common type of treatment for functional amnesia is psychotherapy. Some experts also recommend hypnosis as a way for the patient to recall forgotten events. Exposing the person to common places and people can sometimes help trigger past memories as well. There is little that can be done for patients who suffer from organic amnesia. The brain may eventually recover itself partially, allowing some of the memories to return. However, if the brain cells are permanently damaged, there is no way of turning back the clock. Certain degenerative diseases, including Alzheimer's, usually result in permanent memory loss.