Dissociative amnesia is one of a group of conditions called dissociative disorders. Dissociative disorders are mental illnesses that involve disruptions or breakdowns of memory, consciousness, awareness, identity, and/or perception. When one or more of these functions is disrupted, symptoms can result. These symptoms can interfere with a person's general functioning, including social and work activities, and relationships.

Dissociative amnesia occurs when a person blocks out certain information, usually associated with a stressful or traumatic event, leaving him or her unable to remember important personal information. With this disorder, the degree of memory loss goes beyond normal forgetfulness and includes gaps in memory for long periods of time or of memories involving the traumatic event.

Dissociative amnesia is not the same as simple amnesia, which involves a loss of information from memory, usually as the result of disease or injury to the brain. With dissociative amnesia, the memories still exist but are deeply buried within the person's mind and cannot be recalled. However, the memories might resurface on their own or after being triggered by something in the person's surroundings. There is some debate among professionals as to when “buried” memories may not always be true, and some experts warn against about the risks of “recovering” false traumatic memories.