Dissociative identity disorder (DID), formerly known as multiple-personality disorder, is one of the more controversial diagnoses in the Diagnostic and Statistical Manual of Mental Disorders (fourth edition; DSM-IV), with there being considerable disagreement over the validity and etiology of the disorder. Amnesia between identities is central to a diagnosis of DID. While explicit memory tests often result in amnesic responding in DID patients, more objective memory tests often fail to corroborate self-reports of amnesia between identities. Two perspectives dominate the debate on the cause of DID, with the traditional view proposing that DID manifests as a mechanism for coping with childhood trauma and an alternative sociocognitive perspective suggesting that DID is a response to social demands, with an iatrogenic etiology. The rise in prevalence rates of DID has led to the increased importance of this diagnosis in the court of law. Given the controversy surrounding the validity of the disorder, care should be taken when considering subjective claims of amnesia, as these self-reports are not guaranteed to be substantiated by objective laboratory evidence.
The Diagnosis of Dissociative Identity Disorder
To meet the criteria for a DSM-IV diagnosis of DID, two or more distinct identities must be present who recurrently take control of an individual’s behavior. These alter identities may have distinct personal histories, names, and abilities (e.g., computer proficiency, literacy) and can even vary in professed sex and age. This fractionation of identity must also be accompanied by an inability to recall important personal information, beyond that of ordinary forgetfulness. This memory loss, termed inter-identity amnesia, is thought to result from the compartmentalization of memory within identities and can manifest in many ways, such as gaps in time or the discovery of unfamiliar items in one’s possession.
The properties of inter-identity amnesia can vary. In a one-way amnesia, communication is asymmetrical, as one identity may be omniscient for the experiences of the other but not vice versa. In a two-way amnesia, both identities are unaware of each other’s experiences, memories, and sometimes even existence. A diagnosis of DID cannot be made if the symptoms are due to substance use or a general medical condition. DID is diagnosed more commonly in females than males (from three to nine times more often) and is often diagnosed in individuals with a history of other psychiatric diagnoses. Symptom onset varies, although many individuals report dissociative symptoms dating back to as early as childhood.
As with most other diagnoses, clinicians rely on the self-report of patients when diagnosing DID. This is typically done using either unstructured questioning or a structured interview such as the Structured Clinical Interview for DSM-IV Dissociative Disorders (SCID-D). The Dissociative Experiences Scale (DES) is another common self-report measure of dissociative symptoms, which requires individuals to rate their symptoms on a Likert-type scale, although the DES cannot confirm the diagnosis of DID.
Given the centrality of amnesia to DID, evidence of inter-identity amnesia is essential to a diagnosis. Caution is warranted when interpreting self-reported symptoms of amnesia, however, as research using objective measures of memory reveals an inconsistent picture that does not consistently corroborate the subjective symptoms reported by patients. Studies that have examined memory transfer across identities have provided mixed results, typically finding that some memories are shared between reportedly amnesic identities while other memories are not. It has been proposed that these differences in memory transfer depend on whether the memories are explicit versus implicit. Explicit memory tests require conscious recollection and typically produce amnesia between identities. For example, an amnesic identity may deny any memory of words presented to another identity when asked to recall them. In contrast, implicit memory tasks rely on the premise that prior experiences can influence subsequent behavior independent of conscious awareness— such tasks often show memory transfer. Although the amnesic identity may claim to not recognize the words, given an implicit test, such as a word-stem completion task, he or she may perform in a manner that suggests memory of the words on some level, typically assumed to be implicit and unconscious.
This pattern of amnesia on explicit but not implicit tasks is not unlike that found in organic amnesia. This pattern has alternatively been interpreted as a response to situational expectations, where individuals modify their response patterns in conformance with their expectations about how a person with inter-identity amnesia should respond. Explicit memory tests, unlike implicit tests, are typically obvious assessments of memory, and amnesic responding on explicit tests could result from motivated compliance with expectations. Implicit memory tests, in contrast, tend to be less transparent measures of memory and are less susceptible to manipulation.
Given the inconsistent findings of memory transfer, and also the controversy surrounding the disorder, inter-identity amnesia should ideally be verified by objective tests of inter-identity amnesia that do not rely solely on self-report. Some investigators have attempted to objectively assess memory by using psychophysiological measures such as brain electrical recordings or by creating paradigms where amnesia is difficult to simulate. These methods have typically demonstrated that memories transfer across identities despite self-reports of amnesia. Moreover, one study has suggested that this memory transfer is conscious and explicit. Therefore, although a phenomenological experience of memory loss may be reported by DID patients, this amnesia cannot always be verified by objective memory tests. Given the centrality of inter-identity amnesia to a DID diagnosis and the current reliance on uncorroborated self-report measures, increasing importance needs to be placed on using objective tests of memory to make an accurate diagnosis of DID.
The Controversy around Dissociative Identity Disorder
Controversy surrounds DID, as many skeptics question the validity of the disorder. Research on the properties of inter-identity amnesia has led to conflicting findings, as detailed above. In addition, critics of the disorder highlight the many changes that have occurred in prevalence rates and symptom presentation over time. Historically, DID has been an infrequently diagnosed disorder, with only a handful of cases being reported until the 1900s. However, rates of diagnosis skyrocketed in the 1980s, with prevalence rates numbering in the thousands. DID was popularized in the media around this same time by movies such as The Three Faces of Eve and Sybil. It has been suggested that this exponential increase in diagnoses is mostly circumscribed to specific cultures such as North America, with the majority of diagnoses believed to be attributable to a small percentage of psychologists.
In addition to the increasing prevalence rates, the nature of symptoms has evolved. Earlier DID patients commonly reported only a few identities and often needed a period of transient sleep to switch between identities. In contrast, present-day DID patients typically report approximately 15 alters and the ability to voluntarily switch among identities. These diagnostic, cultural, and symptomatological inconsistencies have incited an ongoing debate about the validity of reported symptoms, resulting in two competing etiological interpretations.
Perspectives on Causal Mechanisms of Dissociative Identity Disorder
Two perspectives dominate the debate on the cause of DID. The posttraumatic interpretation of DID, also termed the disease model, conceptualizes the disorder as a posttraumatic condition resulting from childhood abuse, as the majority of DID patients report a history of child abuse. This perspective suggests that the generation and compartmentalization of multiple identities is manifested as an adaptive strategy that allows the individual to cope with trauma. Consonant with this theory, some DID patients report symptoms similar to those found in posttraumatic stress disorder, such as nightmares, flashbacks, and increased startle responses. The disease theory attributes the rise in prevalence of DID to more accurate diagnoses by clinicians as a result of increased awareness of childhood abuse and its psychiatric sequelae, greater acceptance of the disorder, and a more in-depth focus on previously overlooked symptoms. According to this explanation, certain physicians in specific cultures are becoming sufficiently familiar with the disease to accurately diagnose those symptoms of DID that previously went undiagnosed or misdiagnosed.
Critics of this disease model question the fidelity of memories of abuse reported by DID patients. Such reports are almost exclusively retrospective, and it has been firmly established that childhood memories are susceptible to distortion. In addition, critics suggest that a belief in the disease model may lead clinicians to specifically search for dissociative symptoms in clients with a known history of abuse or for memories of abuse in a client presenting dissociative symptoms, inflating the correlation between DID and memories of abuse. Techniques known to facilitate memory distortion, such as hypnosis, have been used by some clinicians, resulting in questions about the validity of uncovered memories of abuse and the existence of alter identities. Often, memories of abuse are uncovered in therapy, leading many to challenge the veridicality of these memories and point to a theory of a therapist-induced iatrogenic etiology.
An alternative perspective to the disease model, termed the sociocognitive model, proposes that DID is a socially influenced construction that is legitimized and maintained through social interactions. According to this theory, as the disorder has become more widely accepted, DID patients have learned how to present themselves as having multiple identities. Patients form a belief as to how others expect them to act and behave accordingly. This theory suggests that therapists play a large role in the generation and maintenance of this disorder through the use of suggestive questioning, the provision of information about how patients with the disorder should act, and the legitimization of the disorder. This sociocognitive perspective suggests an iatrogenic etiology, proposing that the disorder is generated by the client in response to the suggestive questioning and expectations of the therapist. This view does not assume that a DID patient is consciously faking symptoms but instead speculates that dissociative symptoms are manifested as a way for individuals to view themselves in a way that is congruent with what they believe is expected of them. Often a patient seeks therapy to deal with unspecified psychological distress, and the expression of dissociative symptoms can result in a DID diagnosis, which may bring relief, explanations, and the potential for treatment. Thus, symptoms can be created and experienced by the patient as veridical in that DID patients interpret their normal life experiences from the viewpoint of a fractionated self. According to the sociocognitive model, an increase in the popularity and social acceptance of the disorder has led to greater manifestations of DID symptoms by highly suggestible individuals. Supporting the sociocognitive model, studies have found that alternate personalities can be generated and maintained by individuals with no psychiatric history when undergoing suggestive questioning.
Forensic Implications of Dissociative Identity Disorder
Given the rising numbers of individuals diagnosed with DID, it is no surprise that the controversy surrounding DID has carried over into the courtroom. DID diagnoses have been used as a defense for individuals charged with crimes including kidnapping, forgery, drunk driving, and rape, with varying outcomes. Defendants with DID have pleaded innocent for crimes that they do not remember, purportedly committed by other identities. These defense pleas raise the question as to whether an individual can be held legally responsible for a crime committed by another alter not under the control of the dominant identity. The validity of the DID diagnosis is central to the debate over whether a DID patient should be considered as one unitary individual or as a conglomerate of multiple identities and, in the latter case, whether these distinct identities can be individually and dissociably culpable of a crime. Inter-identity amnesia is another important aspect of this debate, raising the question of whether an individual can be held criminally responsible for a crime committed by another identity of which he or she has no memory or awareness. As demonstrated by the inconsistency in the courtroom verdicts, this debate has not been resolved.
A DID diagnosis has additional ramifications for the legal system. Legal suits have been brought against clinicians for either falsely diagnosing or failing to diagnose the disorder. Alter identities have asked for separate legal representation and have been asked to give sworn testimony. The age of the accused alter identity has also been used as an argument to determine whether the patient is tried in a juvenile or an adult court, and a DID diagnosis can affect decisions about competency to stand trial.
Taking into account the exponential increase in diagnosis rates, it may be that veridical cases of DID are interspersed among many others that do not completely fit the diagnosis and that are the iatrogenic result of misdiagnoses, suggestive therapy, or demand characteristics. Intentional malingering or exaggeration of deficits should also be a consideration, especially in situations with important consequences, as in the case of litigation. Given the controversy over the validity of the disorder, care needs to be taken when making a diagnosis of DID. Self-report measures of memory loss, commonly used for diagnosis, have not always been corroborated by more objective measures of memory, suggesting that the subjective amnesia experienced by the individual may not correspond with the objective experience of amnesia. Thus, caution should be used in evaluating or admitting claims of amnesia in cases of DID, especially in the courtroom where the ramifications of a faulty diagnosis are high. Since inter-identity amnesia is a necessary criterion for a diagnosis of DID and can play an important role in the courtroom, an objective determination of such amnesia is critical and should be necessary to confirm a diagnosis of DID.
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