The lights dimmed at a movie theater about 100 miles northeast of London, in a city of more than 100,000 people. I had traveled nearly 3,500 miles from New York to watch The Three Faces of Eve, a black-and-white movie from 1957. The film, about a woman with multiple personality disorder, is based on a real case study and subsequent book authored by her psychiatrists. In the seat next to me was Lizzie Green*, a woman diagnosed with the same condition, though it’s now called dissociative identity disorder, or DID.
Movies aren’t kind to DID. Fight Club, Sybil, Primal Fear, Hide and Seek, Black Swan, Secret Window, Dr. Jekyll and Mr. Hyde—in films like these, when someone has a hidden personality, it’s usually a violent one that commits unspeakable acts, while the character has no memory of their actions.
“They’re all horror films, aren’t they?” Green, a thin woman in her mid 60s, said to me. “They use a mental disorder to make a very good horror movie.” She paused, and smiled begrudgingly. “I watched Split, and I think it’s a very good film. But I don’t like them doing it.”
Dissociation—a feeling of being disconnected from your thoughts and feelings, often described as seeing yourself from an outside perspective—isn’t rare. According to the US national nonprofit Mental Health America, about a third of all people say they’ve once felt they were watching themselves from afar, as if in a movie.
But when dissociation becomes more extreme, it crosses into surreal territory, becoming Hollywood fodder. Severe dissociation can include psychogenic amnesia, when a person can’t remember personal information with no seeming physical cause, or dissociative fugue state, when a person loses his or her identity altogether—as if they’ve just stepped out of their body and walked away. With DID, it’s more like a person’s body is a boardinghouse filled with many guests, and you’re not quite sure who will come to the door when you knock.
DID affects an estimated .01 to 1 percent of the general population, but it’s a condition that many researchers still disagree on. Its history is fraught with tales of false memories and Satanic cults; only three paragraphs into WebMD’s page on DID, a subheading asks: “Is Dissociative Identity Disorder Real?” To this day, only some believe it is, while others believe it’s a disorder brought on by the power of suggestion and scary stories. Clinicians don’t doubt the suffering of people who get a DID diagnosis, but they can’t agree on where the suffering originates, and that conflict has had major implications for how people with DID are treated.
How does one prove that a mental disorder is “real”? Scientists can look to the brain, case studies, symptoms, and treatments, all to find evidence of a distinct disease. But the disagreements around DID highlight the subjective nature of our categorizations of illness, especially mental ones. Historical context and culture have clearly influenced our understanding of illnesses and their prevalence. In the case of DID, the legacy of multiple personality disorder continues to seep into the work of those treating the disorder as well as those who have it.
In my discussions with people who study DID and treat patients who have it, some said that the diagnosis wasn’t a real thing—that it was just another way to talk about the symptoms of other disorders, like PTSD or bipolar disorder (an illness characterized by mood swings and confusing behavior). Yet others vehemently insisted that DID was a disorder unto itself, perverted by what we’ve seen in the movies but very real, caused by the worst kinds of childhood trauma—such as what Green eventually uncovered in her own mind.
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*The name has been changed to protect the person’s identity because of the sensitive nature of the information she shared.
This article originally appeared on VICE US.