The diagnosis of DID has been heavily debated in the last hundred years. Opinions vary greatly on the topic of DID. In recent years it has become discussed as to whether DID exists and is caused by repeated and severe abuse or whether patients have been simply copying symptoms either they've read about in fictional accounts or that a therapist asked them about while attempting to diagnose them for this condition. Among those who believe such a condition exists there is the additional controversy of whether it should be considered a mental illness or not.
Diagnoses of DID peaked in the mid 1990s and have since declined sharply, a pattern described by Pope et al. as "a brief period of fashion".
Reports of DID are often confirmed by objective evidence and people responsible for these acts might be prone to distort or deny their behavior. The DSM currently treats dissociative amnesia, dissociative fugue, and DID as mental disorders characterized by dissociation. Those who believe that multiple personality is a real phenomenon usually assume that it is a mental disorder, originating in children who are stressed or abused (especially sexually abused). It is presumed that such children may split into several independent personalities as a defense mechanism. DID is attributed to the interaction of overwhelming stress, insufficient childhood nurturing and an innate ability to dissociate memories or experiences from consciousness. Prolonged childhood abuse is believed to be a factor in DID, with a very high percentage of patients reporting documented abuse. DID has been described by Pearson as a severely lasting dissociative response to overwhelming and normally traumatic antecedents and results from childhood trauma. DID has also been found to have consistent diagnostic features.
Some researchers assert that the present scientific evidence is inadequate to support that the suggestive influences in psychotherapy can cause DID and argue that there is little scientific support for hypnosis alone creating DID. One supporter of DID has argued that specialists do not influence their clients to make an increased number of personalities or to develop additional diagnostic criteria. D. Brown has argued that McHugh's publications questioning whether DID exists are "speculation" and claims that McHugh has insufficient clinical experience with DID patients to comment upon the diagnosis. Gleaves states that the research on DID does not support the ideas that DID is a construct of either psychotherapy or the media (the sociocognitive model), but that there is a connection between DID and childhood trauma and that treatment recommendations that follow from the sociocognitive model might be harmful due to the fact that they ignore the posttraumatic symptomology of people with DID.
There is insufficient understanding of consciousness to be able to explain how a novel split would occur in a previously undivided mind and how it would be maintained in the mind. Psychoanalytic theorists believe a schizoid phase of development occurs in childhood, which may have encouraged this view of traumatic splitting. There has been nothing found to explain why children who are later diagnosed with multiple personalities would split from those who do not undergo comparable types of stress.
Dissociative identity disorder is diagnosed in 3 to 4% of people in hospitals for other mental health disorders and a large number of patients in treatment facilities for substance abuse.
Some psychologists and psychiatrists regard DID as being iatrogenic or fictitious, or contend that true cases are extremely rare and that the majority of reported cases are iatrogenic. Drs. Paul McHugh, Herbert Spiegel, A. Piper, H. Merskey are among the leading critics of the DID paradigm and have made their views known in articles and television interviews.
Skeptics contend that those who exhibit the symptoms of MPD/DID have learned to behave as though they had different selves in return for social reinforcement and reward, either from therapists, from other DID patients, or from society at large. The modern DID model relies on the premises that multiplicity is a disorder of memory and that repression of memories is a common defense against childhood sexual abuse and linked to multiplicity. As such, some critics have focused on studies citing the fallibility and flawed nature of human memory, the weaknesses of hypnosis as a tool for recall, and on disproving claims of the accuracy of recovered memories. The work of psychologist Elizabeth Loftus, who specializes in human memory, is usually cited to support this conclusion. Some of Loftus's work, however, has been critiqued in terms of the applicability of its conclusions A more lengthy review of the normal fallacies of memory is given by Nicholas Spanos in his sociocognitive model.
Critics of the DID model point to the fact that the diagnosis of MPD and DID is a phenomenon largely unique to English-speaking countries. Prior to the 1950s, cases of dual personality and multiple personality were occasionally reported and treated as curiosities in the Western world. The 1957 publication of the book The Three Faces of Eve, and the popular movie which followed it, revived the American public's interest in multiple personality. The diagnosis of Multiple Personality Disorder, however, was not included in the DSM until 1980, following the publication in 1974 of the highly influential book Sybil. As media coverage spiked, diagnoses climbed. There were 200 reported cases of MPD from 1880 to 1979, and 20,000 from 1980 to 1990. According to Joan Acocella, 40,000 cases were diagnosed from 1985 to 1995. The DID diagnosis is most common in North America, particularly the United States, and in English-speaking countries more generally. The majority of diagnoses are made by only a few practitioners. There is a controversy around the accuracy of DID reports, as memories of childhood might be able to be distorted and DID patients are easy to hypnotize and are very vulnerable to suggestion in certain situations.
Some take the position that multiplicity can arise in a variety of ways, from being born naturally multiple to dissociating due to trauma; but that regardless of origins, a group of selves can cooperate and function well in tasks of daily living.
Some therapists have found that these allegations derive from a moral panic. As the memories described by some patients identifying with MPD/DID in recovered memory therapy were bizarre, and seemed to strain credibility, or described incidents that could not have happened, the debate over MPD and DID became indelibly linked to the debate over repression for skeptics and critics.
People diagnosed with DID often report that they have experienced severe physical and sexual abuse, especially during their childhood.
A few accused criminals, especially murderers, have claimed one of their "alters" committed a crime and used the diagnosis as a defense. Hillside Strangler Kenneth Bianchi was among the most notable. Dr. Colin Ross was convinced Bianchi was a multiple: however, Chris Costner-Sizemore, brought in to observe Bianchi, stated that in her opinion he was not.
The most recent case on record of an MPD criminal defense was the 1994 trial of Lori Scheirer, a Pennsylvania woman who confessed to a murder because one of her "alters" advised her to do so. She did not say that an "alter" had committed the murder. Scheirer had given enough details to police that she could reasonably be a suspect; but subsequently, she announced that she had made up the entire confession in order to gain attention. Scheirer and other family members related bizarre episodes of memory loss, stating that she looked and acted like totally different people at different times. Her disorder was speculated to have been caused by years of sexual, emotional, and physical abuse, as is usual with MPD claims. Two psychiatrists testified for her defense, one arguing that she had MPD, the other stating that she did not. The defense appeared to work to some extent; she was acquitted.