Dissociative amnesia is classified by the Diagnostic and Statistical Manual of Mental Disorders , 4th Edition, Text Revision, also known as the DSM-IV-TR as one of the dissociative disorders, which are mental disorders in which the normally well-integrated functions of memory, identity, perception, or consciousness are separated (dissociated). The dissociative disorders are usually associated with trauma in the recent or distant past, or with an intense internal conflict that forces the mind to separate incompatible or unacceptable knowledge, information, or feelings. In dissociative amnesia, the continuity of the patient's memory is disrupted. Patients with dissociative amnesia have recurrent episodes in which they forget important personal information or events, usually connected with trauma or severe stress . The information that is lost to the patient's memory is usually too extensive to be attributed to ordinary absentmindedness or forgetfulness related to aging. Dissociative amnesia was formerly called "psychogenic amnesia."
Amnesia is a symptom of other medical and mental disorders; however, the patterns of amnesia are different, depending on the cause of the disorder. Amnesia associated with head trauma is typically both retrograde (the patient has no memory of events shortly before the head injury) and anterograde (the patient has no memory of events after the injury). The amnesia that is associated with seizure disorders is sudden onset. Amnesia in patients suffering from delirium or dementia occurs in the context of extensive disturbances of the patient's cognition (knowing), speech, perceptions, emotions, and behaviors. Amnesia associated with substance abuse, which is sometimes called "blackouts" typically affects only short-term memory and is irreversible. In dissociative amnesia, in contrast to these other conditions, the patient's memory loss is almost always anterograde, which means that it is limited to the period following the traumatic event(s). In addition, patients with dissociative amnesia do not have problems learning new information.
Dissociative amnesia as a symptom occurs in patients diagnosed with dissociative fugue and dissociative identity disorder . If the patient's episodes of dissociative amnesia occur only in the context of these disorders, a separate diagnosis of dissociative amnesia is not made.
Patients with dissociative amnesia usually report a gap or series of gaps in their recollection of their life history. The gaps are usually related to episodes or abuse or equally severe trauma, although some persons with dissociative amnesia also lose recall of their own suicide attempts, episodes of self-mutilation, or violent behavior.
Five different patterns of memory loss have been reported in patients with dissociative amnesia:
- Localized. The patient cannot recall events that took place within a limited period of time (usually several hours or 1–2 days) following a traumatic event. For example, some survivors of the World Trade Center attacks do not remember how they got out of the damaged buildings or what streets they took to get away from the area.
- Selective. The patient can remember some, but not all of the events that took place during a limited period of time. For example, a veteran of D-Day (June 6, 1944) may recall some details, such as eating a meal on the run or taking prisoners, but not others (seeing a close friend hit or losing a commanding officer).
- Generalized. The person cannot recall anything in his/her entire life. Persons with generalized amnesia are usually found by the police or taken by others to a hospital emergency room.
- Continuous. The amnesia covers the entire period without interruption from a traumatic event in the past to the present.
- Systematized. The amnesia covers only certain categories of information, such as all memories related to a certain location or to a particular person.
Most patients diagnosed with dissociative amnesia have either localized or selective amnesia. Generalized amnesia is extremely rare. Patients with generalized, continuous, or systematized amnesia are usually eventually diagnosed as having a more complex dissociative disorder, such as dissociative identity disorder (DID).
Causes and symptoms
The primary cause of dissociative amnesia is stress associated with traumatic experiences that the patient has either survived or witnessed. These may include such major life stressors as serious financial problems, the death of a parent or spouse, extreme internal conflict, and guilt related to serious crimes or turmoil caused by difficulties with another person.
Susceptibility to hypnosis appears to be a predisposing factor in dissociative amnesia. As of 2002, however, no specific genes have been associated with vulnerability to dissociative amnesia.
Some personality types and character traits seem to be risk factors for dissociative disorders. A group of researchers in the United States has found that persons diagnosed with dissociative disorders have much higher scores for immature psychological defenses than normal subjects.
The central symptom of dissociative amnesia is loss of memory for a period or periods of time in the patient's life. The memory loss may take a variety of different patterns, as described earlier.
Other symptoms that have been reported in patients diagnosed with dissociative amnesia include the ollowing:
- Emotional distress related to the amnesia. However, not all patients with dissociative amnesia are distressed. The degree of emotional upset is usually in direct proportion to the importance of what has been forgotten, or the consequences of forgetting.
- Mild depression.
Some patients diagnosed with dissociative amnesia have problems or behaviors that include disturbed interpersonal relationships, sexual dysfunction, employment problems, aggressive behaviors, self-mutilation, or suicide attempts.
Dissociative amnesia can appear in patients of any age past infancy. Its true prevalence is unknown. In recent years, there has been an intense controversy
among therapists regarding the increase in case reports of dissociative amnesia and the accuracy of the memories recovered. Some maintain that the greater awareness of dissociative symptoms and disorders among psychiatrists has led to the identification of cases that were previously misdiagnosed. Other therapists maintain that dissociative disorders are overdiagnosed in people who are extremely vulnerable to suggestion.
It should be noted that psychiatrists in the U.S. and Canada have significantly different opinions of dissociative disorder diagnoses. On the whole, Canadian psychiatrists, both French- and English-speaking, have serious reservations about the scientific validity and diagnostic status of dissociative amnesia and dissociative identity disorder. Only 30% of Canadian psychiatrists think that these two dissociative disorders should be included in the DSM-IV-TR without reservation; and only 13% think that there is strong scientific support for the validity of these diagnoses.
The diagnosis of dissociative amnesia is usually a diagnosis of exclusion. The doctor will take a detailed medical history, give the patient a physical examination, and order blood and urine tests, as well as an electroencephalogram (EEG) or head x ray in order to rule out memory loss resulting from seizure disorders, substance abuse (including abuse of inhalants), head injuries, or medical conditions, such as Alzheimer's disease or delirium associated with fever.
Some conditions, such as age-related memory impairment (AAMI), may be ruled out on the basis of the patient's age. Malingering can usually be detected in patients who are faking amnesia because they typically exaggerate and dramatize their symptoms; they have obvious financial, legal, or personal reasons (such as draft evasion) for pretending loss of memory. In addition, patients with genuine dissociative amnesia usually score high on tests of hypnotizability. The examiner may administer the Hypnotic Induction Profile (HIP) or a similar measure that evaluates whether the patient is easily hypnotized. This enables the examiner to rule out malingering or factitious disorder .
There are several standard diagnostic questionnaires that may be given to evaluate the presence of a dissociative disorder. The Dissociative Experiences Scale, or DES, is a frequently administered self-report screener for all forms of dissociation. The Structured Clinical Interview for the DSM-IV-TR Dissociative Disorders, or SCID-D, can be used to make the diagnosis of dissociative amnesia distinct from the other dissociative disorders defined by the DSM-IV-TR . The SCID-D is a semi-structured interview, which means that the examiner's questions are open-ended and allow the patient to describe experiences of amnesia in some detail, as distinct from simple "yes" or "no" answers.
As of 2002, there are no widely used screeners or diagnostic questionnaires specifically for dissociative amnesia.
Diagnosis of dissociative amnesia in children before the age of puberty is complicated by the fact that inability to recall the first four to five years of one's life is a normal feature of human development. As part of the differential diagnosis, a physician who is evaluating a child in this age group will rule out inattention, learning disorders , oppositional behavior, and psychosis , and seizure disorders or head trauma. To make an accurate diagnosis, several different people (i.e., teachers, therapists, social workers , the child's primary care physician) may be asked to observe or evaluate the child.
Treatment of dissociative amnesia usually requires two distinct periods or phases.
Psychotherapy for dissociative amnesia is supportive in its initial phase. It begins with creating an atmosphere of safety in the treatment room. Very often, patients gradually regain their memories when they feel safe with and supported by the therapist. This rapport does not mean that they necessarily recover their memories during therapy sessions; one study of 90 patients with dissociative amnesia found that most of them had their memories return while they were at home alone or with family or close friends. The patients denied that their memories were derived from a therapist's suggestions, and a majority of them were able to find independent evidence or corroboration of their childhood abuse.
If the memories do not return spontaneously, hypnosis or sodium amytal (a drug that induces a semi-hypnotic state) may be used to help recover them.
After the patient has recalled enough of the missing past to acquire a stronger sense of self and continuity in their life history, the second phase of psychotherapy commences. During this phase, the patient deals more directly with the traumatic episode(s), and recovery from its aftereffects. Studies of the treatments for dissociative amnesia in combat veterans of World War I (1914–1918) found that recovery and cognitive integration of dissociated traumatic memories within the patient's overall personality were more effective than treatment methods that focused solely on releasing feelings.
At present, there are no therapeutic agents that prevent amnestic episodes or that cure dissociative amnesia itself. Patients may, however, be given antidepressants or other appropriate medications for treatment of the depression, anxiety, insomnia , or other symptoms that may accompany dissociative amnesia.
Dissociative amnesia poses a number of complex issues for the legal profession. The disorder has been cited by plaintiffs in cases of recovered memories of abuse leading to lawsuits against the perpetrators of the abuse. Dissociative amnesia has also been cited as a defense in cases of murder of adults as well as in cases of neonatricide (murder of an infant shortly after birth). Part of the problem is the adversarial nature of courtroom procedure in the U.S., but it is generally agreed that judges and attorneys need better guidelines regarding dissociative amnesia in defendants and plaintiffs.
The prognosis for recovery from dissociative amnesia is generally good. The majority of patients eventually recover the missing parts of their past, either by spontaneous re-emergence of the memories or through hypnosis and similar techniques. A minority of patients, however, are never able to reconstruct their past; they develop a chronic form of dissociative amnesia. The prognosis for a specific patient depends on a combination of his or her present life circumstances; the presence of other mental disorders; and the severity of stresses or conflicts associated with the amnesia.
Strategies for the prevention of child abuse might lower the incidence of dissociative amnesia in the general population. There are no effective preventive strategies for dissociative amnesia caused by traumatic experiences in adult life in patients without a history of childhood abuse.
See also Abuse
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International Society for the Study of Dissociation (ISSD). 60 Revere Drive, Suite 500, Northbrook, IL 60062. (847) 480-0899. Fax: (847) 480-9282. <www.issd.org> .
National Institute of Mental Health. 6001 Executive Boulevard, Room 8184, MSC 9663, Bethesda, MD 20892-9663. (301) 443-4513. <www.nimh.nih.gov> .
National Organization for Rare Disorders, Inc. P. O. Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518. <www.rarediseases.org> .
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Special issue of Ethics and Behavior 8 (1998). "Symposium: Science and Politics of Recovered Memories." The issue is based on a program chaired by Gerald Koocher of Harvard Medical School at the 1998 convention of the American Psychiatric Association.
Rebecca J. Frey, Ph.D.