Among the hundreds of disorders defined by the American Psychiatric Association, dissociative identity disorder, formerly called multiple personality disorder, is one of the more contentious.
Herschel Walker's public announcement brings the disorder back into the public eye. ABC News polled mental health experts to get their reaction.
Controversy exists because it calls into question people's understanding of personality, according to mental health experts. How can someone walk around as a "we" instead of an "I"?
Experts still debate whether the disorder should have ever been included in the Diagnostic and Statistical Manual of Mental Disorders, the psychiatric medical bible. To Dr. Richard Loewenstein, medical director of the Trauma Disorders Program at Sheppard Pratt Health Systems in Baltimore, including the disorder inclusion marked "an important watershed in psychiatric history," but to Dr. Mark Levy, a distinguished life fellow at the American Psychiatric Association and assistant clinical professor psychiatry at the University of California at San Francisco, its inclusion "was a mistake."
Dr. John H. Casada, assistant professor of psychiatry at the University of Texas Health Science Center at San Antonio, takes a middle ground, saying "the disorder was appropriately included in the DSM but needs refinement to make the diagnosis more specific."
Most experts ABC News contacted agreed that the disorder exists, and that it probably occurs in about 1 percent of the population. Many expressed concern that DID or multiple personality can be misdiagnosed, however, and a few believe it rarely, if ever, occurs. Here are the different schools of thought on the disorder.
"It probably isn't real," Levy said. "Dissociation is real. It occurs after trauma in some people and in psychosis, like schizophrenia. However, I've never seen a so-called multiple personality in 35 years of practice."
Casada, of the University of Texas Health Science Center, said, "Such extreme claims demand extraordinary proof. The true believers will be more apt to diagnose the illness and will require less clear symptoms. The skeptics, of which I am admittedly one, will require more evidence and clearer evidence before we diagnose what we believe to be a very rare disorder. I believe that most currently diagnosed DID is caused by clinicians."
Dr. Carole Lieberman, a psychiatrist in Beverly Hills, Calif., suggested that patients might use the disorder to excuse their actions. "Psychiatrists must make the diagnosis of dissociative identity disorder very carefully, because oftentimes patients want to find an excuse for their behavior by attributing it to a 'disorder' rather than their own impulsive mistakes."
"The diagnosis of DID is not controversial," said Dr. J. Douglas Bremner, professor of psychiatry and radiology at Emory University School of Medicine in Atlanta. "It is established in the DSM. Prior media coverage may have confused the issue."
Some clinicians say they have treated many people with DID, including Walker's therapist, Jerry Mungadze, and Sheppard Pratt's Loewenstein.