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Dissociative Amnesia

by David Spiegel, MD

Dissociative amnesia is amnesia caused by trauma or stress, resulting in an inability to recall important personal information.

  • People have gaps in their memory, which may span a few minutes to decades.

  • After tests are done to rule out other possible causes, doctors diagnose the disorder based on symptoms.

  • Memory retrieval techniques, including hypnosis and drug-facilitated interviews, are used to fill in the memory gaps.

  • Psychotherapy is needed to help people deal with the experiences that triggered the disorder.

Amnesia is the total or partial inability to recall recent experiences or ones from the distant past. When amnesia is caused by a psychologic rather than a physical disturbance, it is called dissociative amnesia.

In dissociative amnesia, the lost memory usually involves information that is normally part of routine conscious awareness or autobiographic memory:

  • Who one is

  • Where one went

  • To whom one spoke

  • What one did, said, thought, and felt

Often, it is information about traumatic or stressful events, such as childhood abuse. Sometimes the information, though forgotten, continues to influence behavior. For example, even though a woman who was raped in an elevator cannot recall any details of the assault, she nonetheless avoids elevators and is unwilling to enter them.

The disorder is more common among women than men, usually people who have experienced or witnessed traumatic events, such as physical or sexual abuse, rape, wars, genocide, accidents, natural disasters, or death of a loved one.

Dissociative amnesia can persist for some time after a traumatic event. Sometimes people appear to spontaneously recover memories. Unless confirmed by another person or other evidence, how closely and accurately such recovered memories reflect real events from the past may be unclear.

Symptoms of Dissociative Amnesia

The most common symptom is memory loss.

Memory loss may involve any of the following:

  • A specific event or events or a specific period of time, such as the months or years of being abused as a child or the days spent in intense combat (localized amnesia)

  • Only certain aspects of an event or only certain events during a period of time (selective amnesia)

  • Personal identity and entire life story, sometimes including well-learned skills and information about the world (generalized amnesia)

  • Information in a specific category, such as all information about a particular person or about their family (systematized amnesia)

  • Each new event as it occurs (continuous amnesia)

Generalized amnesia is rare. It is more common among combat veterans, people who have been sexually assaulted, and people experiencing extreme stress or conflict. It usually begins suddenly.

Amnesia may not appear immediately after a traumatic or stressful event. It may take hours, days, or longer to appear.

Shortly after loss of memory, some people seem confused. Some are very distressed. Others are strangely indifferent.

Most people with dissociative amnesia have one or more gaps in their memory. Gaps usually span a few minutes to a few hours or days but may span years, decades, or even an entire life. Most people are unaware or only partly aware that they have gaps in their memory. They become aware only later, when memories reappear or they are confronted with evidence of things that they have done but do not recall.

Affected people have difficulty forming and maintaining relationships.

Some people have flashbacks, as occur in posttraumatic stress disorder ( PTSD). That is, they relive events as if they were actually happening, and they are unaware of their subsequent personal history—for example, that they survived the trauma. Flashbacks may alternate with amnesia for what happened during the flashback. Some people with dissociative amnesia develop PTSD later, especially when they become aware of the traumatic or stressful events that triggered their amnesia.

People may also have vague symptoms, such as fatigue, weakness, or problems sleeping. Depression and suicidal and other self-destructive behaviors (such as substance abuse and reckless sexual behavior) are common. Risk of suicidal behaviors may be increased when amnesia resolves suddenly and people are overwhelmed by traumatic memories.

Rarely, people with an extreme form of dissociative amnesia suddenly travel from their home for a period of time. During this time, they do not remember some or all of their past life, including who they are (their identity). These episodes are called dissociative fugues.

Diagnosis of Dissociative Amnesia

  • A doctor's evaluation

  • Sometimes tests to rule out other possible causes

Doctors diagnose the disorder based on the person’s symptoms. They also do a physical examination to exclude neurologic causes of amnesia such as dementia. Tests are sometimes needed to exclude other causes of amnesia. Tests include the following:

  • Magnetic resonance imaging (MRI) or computed tomography (CT) to rule out brain tumors and other structural brain disorders

  • Electroencephalography (EEG) to rule out a seizure disorder

  • Blood tests for toxins and drugs to rule out, for example, use of recreational or illegal drugs

A psychologic examination is also done. Special psychologic tests often help doctors better characterize and understand the person’s dissociative experiences and thus develop a treatment plan.

Prognosis

Sometimes memories return quickly, as can happen when people are taken out of the traumatic or stressful situation (such as combat). In other cases, amnesia, particularly in people with dissociative fugue, persists for a long time. Symptoms may decrease as people age.

Most people recover what appears to be their missing memories and resolve the conflicts that caused the amnesia. However, some people never break through the barriers that prevent them from reconstructing their missing past.

Treatment of Dissociative Amnesia

  • A supportive environment

  • Sometimes memory retrieval techniques (such as hypnosis)

  • Psychotherapy

Supportive environment

Doctors begin treatment by helping people feel safe and secure—for example, by helping them to avoid further traumatization. If people have no apparent urgent reason to recover the memory of a painful event, this supportive treatment may be all that is needed. People may gradually recall the missing memories.

Memory retrieval techniques

If the missing memories are not recalled or if the need to recall the memories is urgent, memory retrieval techniques are often successful. They include

  • Hypnosis

  • Drug-facilitated interviews (interviews conducted after a sedative, such as a barbiturate or benzodiazepine, is given intravenously)

Doctors use hypnosis and drug-facilitated interviews to reduce the anxiety associated with the period for which there are gaps in memory and to penetrate or bypass the defenses people have created to protect themselves from recalling painful experiences or conflicts.

However, doctors must be careful not to suggest what should be recalled (and thus create a false memory) or to cause extreme anxiety. Furthermore, memories recalled through such techniques may not be accurate and may require confirmation from another person or source. Therefore, before hypnosis or a drug-facilitated interview, doctors inform people that memories retrieved with these techniques may or may not be accurate and ask for consent to proceed.

Filling in the memory gap to the greatest extent possible helps restore continuity to personal identity and sense of self.

Psychotherapy

Once amnesia has resolved, continued psychotherapy helps people do the following:

  • Understand the trauma or conflicts that caused the disorder

  • Find ways to resolve them

  • Avoid future traumatization if possible

  • Move on with their life