Mental Disorders/Phobias

Dissociative identity disorder

Dissociative identity disorder (DID), previously known as multiple personality disorder (MPD), is a mental disorder characterized by at least two distinct and relatively enduring identities or dissociated personality states that alternately show in a person's behavior, accompanied by memory impairment for important information not explained by ordinary forgetfulness. These symptoms are not accounted for by substance abuse, seizures, other medical conditions, nor by imaginative play in children. Diagnosis is often difficult as there is considerable comorbidity with other mental disorders. Malingering should be considered if there is possible financial or forensic gain, as well as factitious disorder if help-seeking behavior is prominent.

DID is one of the most controversial psychiatric disorders, with no clear consensus on diagnostic criteria or treatment. Research on treatment efficacy has been concerned primarily with clinical approaches and case studies. Dissociative symptoms range from common lapses in attention, becoming distracted by something else, and daydreaming, to pathological dissociative disorders. No systematic, empirically supported definition of "dissociation" exists.

Although neither epidemiological surveys nor longitudinal studies have been conducted, it is generally believed that DID rarely resolves spontaneously. Symptoms are said to vary over time. In general, the prognosis is poor, especially for those with comorbid disorders. There are few systematic data on the prevalence of DID. The International Society for the Study of Trauma and Dissociation states that the prevalence is between 1 and 3% in the general population, and between 1 and 5% in inpatient groups in Europe and North America. DID is diagnosed more frequently in North America than in the rest of the world, and is diagnosed three to nine times more often in females than in males. The prevalence of DID diagnoses increased greatly in the latter half of the 20th century, along with the number of identities (often referred to as "alters") claimed by patients (increasing from an average of two or three to approximately 16). DID is also controversial within the legal system, where it has been used as a rarely successful form of the insanity defense. The 1990s showed a parallel increase in the number of court cases involving the diagnosis.

Dissociative disorders including DID have been attributed to disruptions in memory caused by trauma and other forms of stress, but research on this hypothesis has been characterized by poor methodology. So far, scientific studies, usually focusing on memory, have been few and the results have been inconclusive. An alternative hypothesis for the cause of DID is as a by-product of techniques employed by some therapists, especially those using hypnosis, and disagreement between the two positions is characterized by intense debate. DID became a popular diagnosis in the 1970s, 80s and 90s, but it is unclear if the actual rate of the disorder increased, if it was more recognized by health care providers, or if sociocultural factors caused an increase in therapy-induced (iatrogenic) presentations. The unusual number of diagnoses after 1980, clustered around a small number of clinicians and the suggestibility characteristic of those with DID, support the hypothesis that DID is therapist-induced. The unusual clustering of diagnoses has also been explained as due to a lack of awareness and training among clinicians to recognize cases of DID.

Dissociation, the term that underlies the dissociative disorders including DID, lacks a precise, empirical, and generally agreed upon definition. A large number of diverse experiences have been termed dissociative, ranging from normal failures in attention to the breakdowns in memory processes characterized by the dissociative disorders. Thus it is unknown if there is a common root underlying all dissociative experiences, or if the range of mild to severe symptoms is a result of different etiologies and biological structures. Other terms used in the literature, including personality, personality state, identity, ego state and amnesia, also have no agreed upon definitions. Multiple competing models exist that incorporate some non-dissociative symptoms while excluding dissociative ones. The most widely used model of dissociation conceptualizes DID as at one extreme of a continuum of dissociation, with flow at the other end, though this model is being challenged.

Some terms have been proposed regarding dissociation. Psychiatrist Paulette Gillig draws a distinction between an "ego state" (behaviors and experiences possessing permeable boundaries with other such states but united by a common sense of self) and the term "alters" (each of which may have a separate autobiographical memory, independent initiative and a sense of ownership over individual behavior) commonly used in discussions of DID. Ellert Nijenhuis and colleagues suggest a distinction between personalities responsible for day-to-day functioning (associated with blunted physiological responses and reduced emotional reactivity, referred to as the "apparently normal part of the personality" or ANP) and those emerging in survival situations (involving fight-or-flight responses, vivid traumatic memories and strong, painful emotions, the "emotional part of the personality" or EP). "Structural dissociation of the personality" is used by van der Hart and colleagues to distinguish dissociation they attribute to traumatic or pathological causes, which in turn is divided into primary, secondary and tertiary dissociation. According to this hypothesis, primary dissociation involves one ANP and one EP, while secondary dissociation involves one ANP and at least two EPs and tertiary dissociation, which is unique to DID, is described as having at least two ANP and at least two EP. Others have suggested dissociation can be separated into two distinct forms, detachment and compartmentalization, the latter of which, involving a failure to control normally controllable processes or actions, is most evident in DID. Efforts to psychometrically distinguish between normal and pathological dissociation have been made, but they have not been universally accepted.

According to the fifth Diagnostic and Statistical Manual of Mental Disorders (DSM-5), DID symptoms include "the presence of two or more distinct personality states" accompanied by the inability to recall personal information, beyond what is expected through normal forgetfulness. Other DSM-5 symptoms include a loss of identity as related to individual distinct personality states, and loss referring to time, sense of self and consciousness. In each individual, the clinical presentation varies and the level of functioning can change from severely impaired to adequate. The symptoms of dissociative amnesia are subsumed under the DID diagnosis but can be diagnosed separately. Individuals with DID may experience distress from both the symptoms of DID (intrusive thoughts or emotions) and the consequences of the accompanying symptoms (dissociation rendering them unable to remember specific information). The majority of patients with DID report childhood sexual or physical abuse, though the accuracy of these reports is controversial. Identities may be unaware of each other and compartmentalize knowledge and memories, resulting in chaotic personal lives. Individuals with DID may be reluctant to discuss symptoms due to associations with abuse, shame, and fear. DID patients may also frequently and intensely experience time disturbances.

The number of identities varies widely, with most patients identifying fewer than ten, though as many as 4,500 have been reported. The average number of identities has increased over the past few decades, from two or three to now an average of approximately 16. However, it is unclear whether this is due to an actual increase in identities, or simply that the psychiatric community has become more accepting of a high number of compartmentalized memory components. The primary identity, which often has the patient's given name, tends to be "passive, dependent, guilty and depressed" with other personalities being more active, aggressive or hostile, and often containing a current time line that lacks childhood memory. Most identities are of ordinary people, though fictional, mythical, celebrity and animal parts have been reported.