Dissociation and Dissociative Disorders

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Dissociation and Dissociative Disorders




Types of dissociative disorders




The dissociative disorders are a group of mental disorders that affect consciousness and are defined as causing significant interference with the patient’s general functioning, including social relationships and employment.


Dissociation is a mechanism that allows the mind to separate or compartmentalize certain memories or thoughts from normal consciousness. These split-off mental contents are not erased. They may resurface spontaneously or be triggered by objects or events in the person’s environment.

Until recently, dissociation was widely considered to be a process that occurs along a spectrum of severity. It was considered a spectrum because people experiencing dissociation do not necessarily always have a dissociative disorder or other mental illness. A mild degree of dissociation occurs with some physical stressors; people who have gone without sleep for a long period of time, have had “laughing gas” for dental surgery, or have been in a minor accident often have brief dissociative experiences. As well, in another commonplace example of dissociation, people completely involved in a book or movie may not notice their surroundings or the passage of time. Yet another example might be driving on the highway and passing several exits without noticing or remembering. Dissociation is related to hypnosis in that hypnotic trance also involves a temporarily altered state of consciousness. Most patients with dissociative disorders are highly hypnotizable.

People in other cultures sometimes have dissociative experiences in the course of religious or other group activities (in certain trance states). These occurrences should not be judged in terms of what is considered “normal” in the United States.

Rather than the pathological forms of the disorder being considered a continuum, they now have been dichotomized into the categories of detachment and compartmentalization. Specific characteristics distinguish each of these, although there can be overlap. For example, compartmentalization might be characteristic of a form of dissociative disorder called dissociative amnesia. Patients who have the compartmentalized type of dissociation do not engage in conscious integration of mental systems and do not or cannot consciously access certain areas of memory or information that normally would be available. This type of dissociation also can occur in conversion disorder.

A person exhibiting the detachment form of a dissociation disorder experiences the altered state of consciousness that is more commonly associated with the concept of dissociation. In such cases, derealization or depersonalization are not merely transient, brief manifestations caused by lack of sleep. Instead, people with dissociation disorder may exhibit a flat affect (outward presentation of mood or emotion) and have a sense of being out of their own bodies. These detachment forms of dissociation may be associated with trauma and post-traumatic stress disorder , although post-traumatic stress disorder may also elicit crossover symptoms of compartmentalization. Recent studies of trauma indicate that the human brain stores traumatic memories in a different way than normal memories. Traumatic memories are not processed or integrated into a person’s ongoing life in the same fashion as normal memories. Instead they are dissociated, or “split off,” and may erupt into consciousness from time to time without warning. Affected people cannot control or “edit” these memories. Over a period of time, these two sets of memories, the normal and the traumatic, may coexist as parallel sets without being combined or blended. It has been suggested that the detachment may interfere with this process of consolidation. In extreme cases, different sets of dissociated memories may cause people to develop separate personalities for these memories—a disorder known as dissociative identity disorder (formerly called multiple personality disorder).


Studies suggest a frequency of pathological dissociation in the general North American population of between 2% and 3.3%. In Europe, reported rates are lower, at 0.3% in the nonclinical population and between 1.8% and 2.9% in student populations. Among psychiatric patients, frequency is much higher, between 5.4% and 12.7%, and it also is higher in groups with specific psychiatric diagnoses; for example, its frequency among women with eating disorders can be as high as 48.6%.

Types of dissociative disorders

Dissociative amnesia

Dissociative amnesia is a disorder in which the distinctive feature is the patient’s inability to remember important personal information to a degree that cannot be explained by normal forgetfulness. In many cases, it is a reaction to a traumatic accident or witnessing a violent crime. Patients with dissociative amnesia may develop depersonalization or trance states as part of the disorder, but they do not experience a change in identity.

Dissociative fugue

Dissociative fugue is a disorder in which those affected temporarily lose their sense of personal identity and travel to other locations where they may assume a new identity. Again, this condition usually follows a major stressor or trauma. Apart from inability to recall their past or personal information, patients with dissociative fugue do not behave strangely or appear disturbed to others. Cases of dissociative fugue are more common in wartime or in communities disrupted by a natural disaster.

Depersonalization disorder

Depersonalization disorder is a disturbance in which the patient’s primary symptom is a sense of detachment from the self. Depersonalization as a symptom (not as a disorder) is quite common in college-age populations. It is often associated with sleep deprivation or “recreational” drug use. It may be accompanied by “derealization” (where objects in an environment appear altered). Patients sometimes describe depersonalization as feeling like a robot or watching themselves from the outside. Depersonalization disorder may also involve feelings of numbness or loss of emotional “aliveness.”

Dissociative identity disorder (DID)

Dissociative identity disorder (DID) is considered the most severe dissociative disorder and involves all of the major dissociative symptoms. People with this disorder have more than one personality state, and the personality state controlling the person’s behavior changes from time to time. Often, a stressor will cause the change in personality state. The various personality states have separate names, temperaments, gestures, and vocabularies. This disorder is often associated with severe physical or sexual abuse, especially abuse during childhood. Women are diagnosed with this disorder more often than men.


Amnesia —A general medical term for loss of memory that is not due to ordinary forgetfulness. Amnesia can be caused by head injuries, brain disease, or epilepsy, as well as by dissociation. Depersonalization—A dissociative symptom in which patients feel that their bodies are unreal, are changing, or are dissolving.

Derealization —A dissociative symptom in which the external environment is perceived as unreal.

Dissociation —A reaction to trauma in which the mind splits off certain aspects of the traumatic event from conscious awareness. Dissociation can affect the patient’s memory, sense of reality, and sense of identity.

Fugue —A dissociative experience during which those affected travel away from home, have amnesia regarding their past, and may be confused about their identity but otherwise appear normal.

Hypnosis —The means by which a state of extreme relaxation and suggestibility is induced. Hypnosis is used to treat amnesia and identity disturbances that occur in dissociative disorders.

Multiple personality disorder (MPD) —An older term for dissociative identity disorder (DID).

Trauma —A disastrous or life-threatening event that can cause severe emotional distress, including dissociative symptoms and disorders.

Dissociative disorder not otherwise specified (DDNOS)

DDNOS is a diagnostic category ascribed to patients with dissociative symptoms that do not meet the full criteria for a specific dissociative disorder.


Studies now suggest that treatment of a specific dissociation disorder should be based on whether or not the manifestations are considered as the compartmentalized type or the detachment type. Treatment

recommendations for the compartmentalized types of disorders include focusing on reactivating and integrating the isolated mental compartments, possibly through hypnosis. To address detachment-based dissociation, therapies may include identifying triggers for the detached state, and determining how to stop the triggers and/or stop the detached condition when it is triggered. Standard approaches for these tactics may include cognitive-behavioral therapy .



American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed., Text rev. Washington, D.C.: American Psychiatric Association, 2000.


Spitzer, Carsten, and others. “Recent Developments in the Theory of Dissociation.” World Psychiatry 5 (2006): 82–86.


American Psychiatric Association. 1400 K Street NW, Washington, DC 20005. Telephone: (888) 357-7924. Fax: (202) 682-6850.

The International Society for the Study of Dissociation. 8201 Greensboro Drive, Suite 300, McLean, VA 22102. Telephone: (703) 610-9037, Fax: (703) 610-9005. <http://www.issd.org/index_actual.html>.


The Mayo Clinic. “Dissociative Disorders.” <http://www.mayoclinic.com/health/dissociative-disorders/DS00574/DSECTION=5>.

New York Online Access to Health (NOAH). “Dissociative Disorders.” 2006. <http://www.noah-health.org/en/mental/disorders/dissociative.html>.

U.S. Department of Health and Human Services. “Dissociation.” <http://www.womenshealth.gov/wwd/conditions/dissociative.cfm?style=module>.

Rebecca J. Frey, PhD

Emily Jane Willingham, PhD