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Definition: multiple personality disorder from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Psychiatric disorder wherein the patient exhibits two or more personalities. Personalities can be widely differing, with the same patient switching between the personalities of children and adults of different ages, sexes, and temperaments. Each personality is distinct, and often unaware of the others. MPD may occur as a result of child abuse, though not all psychiatrists accept that it is a genuine disorder.

Summary Article: DISSOCIATIVE IDENTITY DISORDER AND TRAUMA from Encyclopedia of Trauma

Dissociative identity disorder (DID) is a psychological disorder that is included in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders under the category of Dissociative Disorders. DID is estimated to afflict from 1% to 3% of the population and occurs in cases of severe childhood trauma, such as ongoing childhood sexual abuse and/or severe physical abuse and thus is included as a trauma disorder. This entry presents a description of DID, followed by discussion of alternate identities that an individual with DID experiences, common comorbidities, causes of the disorder, iatrogenesis, and a brief summary of treatment goals and processes.

Description of Dissociative Identity Disorder

Individuals who meet criteria for DID experience the existence of two or more distinct identities or personality states (referred to as alternate identities), with the number of reported identities ranging from 2 to over 100. In most cases, there is a primary identity that uses the person's birth name, and this identity is often described as passive, dependent, guilty, and depressed. The alternate identities often have characteristics that are different from the primary identity. In contrast to those with DID, most individuals without psychological disorder tend to experience the existence of a single, unitary identity or sense of self that is more or less stable across time. Even though individuals without DID may experience some fluctuations in how they perceive and feel about themselves in different circumstances, they experience themselves as one person, as opposed to two or more distinct persons. With DID, each of the identities has its own unique way of perceiving and relating to the self, to others, and to the environment. At any given time, the individual's behavior is controlled by one of these personality states, and the personality states may transition from one state to another in sequence.

The person with DID is unable to remember important information about himself or herself, which is not the normal forgetfulness that everyone experiences from time to time. For example, while a person without DID may forget what she did on her birthday 10 years ago, a person with DID may not remember anything about what happened yesterday afternoon, may not remember buying the dress hanging in the closet that she purchased last week, may not remember meeting the person she met that morning, and so forth. Persons with DID tend to be highly hypnotizable. DID is not limited to North American culture but has been found in a wide variety of cultures from around the world. It is diagnosed three to nine times more often in women than men, and females tend to have a higher number of alternate identities than males. DID is more common among first-degree biological relatives.

Alternate Identities

Alternate identities are parts of the personality that are not connected to each other (are dissociated) in the subjective experience of the individual. They may be of varying ages and genders, with widely varying vocabulary, thoughts, memories, attitudes, behaviors, feelings, and interpersonal patterns of relating. Patients with DID may refer to these alternative identities by different terms, including parts, aspects, selves, multiples, and so forth. They may report varying levels of awareness of existence of other identities, ranging from no awareness to complete awareness; they may be critical of each other and may be in conflict with each other. For example, one identity may verbalize much animosity toward another identity, and vice versa.

Case reports indicate that separate identities can have different handwriting and disparities in physiological processes. For example, different identities may vary in their degree of visual acuity, heart rate, blood pressure, EEG patterns, and in their responses to the same medication. Different identities of a diabetic may have different glucose levels. Some research studies have found significantly different psycho-physiological responses between alternate identities in comparison to controls (individuals who do not have DID) who were instructed by the researcher to simulate different personality states. Differences were found in visually evoked brain potentials, galvanic skin responses to stimuli, electroencephalographs (EEGs), muscle tension, immune function, functional magnetic resonance imaging (MRI) activation, and visual acuity.

There are gaps in memory reported by persons with DID, and the amnesia occurs for both recent events and events in the past. Some identities have very constricted memories, whereas those that are more controlling have more complete memories. Some identities that are not in control may gain control to consciousness by using auditory or visual hallucinations, such as a voice telling the person what to do. Observers, such as family members, may comment on a person's actions of which the person has no recollection. Stressors often lead to transitions between identities, and the transitions usually occur in seconds but may be longer. Transitions between identities may be evidenced with rapid blinking, facial changes, voice or demeanor changes, and shifts in the person's train of thought.

Related Disorders and Symptoms

Individuals with DID often have symptoms of other disorders, including posttraumatic stress disorder (PTSD), self-injury, suicidal behavior, aggression, revictimization in relationships, depression, panic, somatoform disorders, substance-related disorders, sleep disorders, and eating disorders. Such comorbidity often makes diagnosis difficult and treatment more lengthy and complicated.

Developmental Etiological Models

What causes DID? Developmental models are based in the premise that DID is caused by severe trauma and disrupted attachment, which prevents the development of a unified sense of self. DID does not occur as a result of a coherent sense of self being shattered by trauma (such as that which occurs with some adult traumas), but DID entails the prevention of the development of a coherent sense of self.

Research has shown that individuals who meet diagnostic criteria for DID tend to have documented or self-reported histories of extreme trauma and abuse during childhood. Many theorists view the development of alternate identities as occurring when a young child, particularly prior to age 5, does not develop a unified sense of self because of severe trauma that is coupled with unhealthy attachments based in disturbed caretaking. Those who do not have DID develop a unified sense of self that persists across time and context. DID rarely begins after adult traumatic experiences in the absence of a history of childhood trauma.

It is thought by many theorists that distinct identities contain distinct traumatic memories and emotions that are kept away (dissociated) from conscious awareness so that the child can function in day-to-day life. For example, if a child were flooded with traumatic memories and affects from a severe rape by his or her father and an absence of soothing caretaking, he or she would have great difficulty learning at school. When those memories and feelings are contained by an alternate identity and kept out of awareness, the child can function better at school.

Many also believe that DID develops in the context of unhealthy parenting and disturbed child-caretaker attachments. This may interfere with the child's ability to integrate different experiences into one unified sense of self. Dissociation of disturbed parenting experiences may preserve attachment to the caregiver and help the child to survive an otherwise intolerable life. The result of severe abuse in the context of disturbed attachment relationships with caregivers may be a wide number of identity states, with different degrees of separateness, that develop over early childhood, middle childhood, and adolescence.

Assessment/Measures of DID

There are various self-report measures to assess for dissociation, including DID. In addition, there are some semi-structured and structured interviews. A complete discussion of assessment measures is beyond the scope of this entry.

The Question of Iatrogenesis

The diagnosis and existence of DID is controversial. Some argue that DID is a diagnosis that occurs as a result of therapists imposing the diagnosis on vulnerable and easily influenced individuals during treatment. In this iatrogenic view, the individual patient then exhibits symptoms based on the influence of theorists and clinicians. This point of view is similar to that of proponents of the False Memory Foundation, who argue that many cases of recovered memories of childhood sexual abuse are false. However, there are no clinical or empirical data to support the iatrogenesis argument.

This is not to say that false diagnosis cannot occur in other ways, however, and individuals can be misdiagnosed with DID when they do not meet criteria for the disorder. The symptoms of other disorders can give rise to patient behaviors and self-reports that sound like DID, when in fact they are not due to DID. Some symptoms of DID also occur in other dissociative disorders, may occur in PTSD, somatization disorder, personality disorder, bipolar disorder, psychosis with delusions, and others. This can make accurate diagnosis difficult. Also, when under hypnosis, a patient may exhibit behaviors and experiences that appear to reflect DID but do not. Moreover, persons may malinger DID when they are not really suffering from it. This may be especially the case in legal contexts. Individuals may also behave in a manner that is consistent with DID and believe they suffer from DID, based in factitious presentations. That is, the patient is benefiting in some manner by believing that he or she has DID.


The clinical course of DID tends to fluctuate but is chronic and recurrent. It usually takes around 7 years before a diagnosis is made after the person first presents for treatment. The symptoms may be less manifest as the individual ages but often recur when under stress or with trauma or substance abuse.

Clinicians are advised to view the DID patient as a single person who experiences separate states of relatively independent identities. These states or identities may take control of the individual's body and influence the person's behavior and experience. Clinicians should view the patient as a whole adult person with alternate identities sharing responsibility for the person's life. The whole person is to be held accountable for the actions of the identities, even when there is amnesia or loss of control of behavior.

Treatment Goals

Most experts view the ultimate goal of treatment of individuals with DID as better integrated functioning, with increased communication among the identities and better coordination of behavior. All of the identities are to be viewed as equals in terms of importance or "realness," and no identity should be encouraged to be more autonomous or developed than others. None of the alternate identities should be ignored or disposed of. Patients are taught to view the identities as reflecting maladaptive coping mechanisms as a result of traumas. An important component of treatment is teaching the identities more effective skills for coping. Some clinicians believe complete fusion of alternate identities is the ultimate goal of treatment; however, this is not always possible for patients to attain, and some patients do not desire fusion. As such, the goal of cooperation in terms of vocation, interpersonal relationships, and psychological functioning is encouraged. Fusion refers to the complete merging of two identities into one identity that holds the qualities of both identities. Final fusion occurs when all identities fuse into one. Integration, on the other hand, refers to an ongoing process that occurs prior to fusion and consists of undoing all aspects of separateness. Integration persists through fusion and beyond. Outcome data suggests that individuals with DID can be successfully treated.

Phase-Oriented Treatment

Most experts in the area of severe childhood abuse trauma and attachment disruption emphasize a phase-oriented treatment approach. In the first phase, safety, stabilization, and symptom reduction are the primary focus. In subsequent stages, processing of traumatic memories occurs, followed by identity integration and rehabilitation. During the first phase, patients are provided with psychoeducation where they learn about the disorder, learn to understand, accept, and access the different identity states, and learn to interact and communicate with them. It is imperative to do this in a safe manner, early in the treatment. The identities are accessed using both direct and indirect means.

At minimum, 3 to 5 years of treatment is required, and therapy may last for two decades or more with very severe cases. Treatment consists of individual therapy using various modalities; however, inpatient treatment may be needed during crises. Group therapy is not a viable primary treatment, but specialized groups may be useful adjuncts to individual treatment, especially skills-training groups. Medications are not a primary treatment but may be useful adjuncts for comorbid disorders or symptoms such as PTSD. It is important for clinicians to be aware that different identities may have different reactions to a medication. Individuals with DID, with appropriate treatment, often go on to live rewarding and successful lives.

See also Childhood Traumatic Stress; Complex Trauma; Dissociation

Further Readings
  • Chu, J. (1998). Riding the therapeutic roller coaster: Stage-oriented treatment for survivors of child abuse. In Chu, J. A. (Ed.), Rebuilding shattered lives: The responsible treatment of complex post traumatic and dissociative disorders (pp. 75-91). New York, NY: Wiley.
  • International Society for the Study of Dissociation. (2005). Guidelines for treating dissociative identity disorder in adults. Journal of Trauma & Dissociation, 6(4), 69-149.
  • Liotti, G. (2006). A model of dissociation based on attachment theory and research. Journal of Trauma and Dissociation, 7(4), 55-73.
  • Pica, M. (1999). The evolution of alter personality states in dissociative identity disorder. Psychotherapy, 36(4), 404-415.
Anne Dietrich
2012 © SAGE Publications, Inc

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