ABOVE: Clara Norton Fowler (pseudonym: Christine Beauchamp) was treated by Morton Prince at the turn of the 20th century. Prince identified several personalities in Beauchamp over the years, but was particularly fascinated by “Sally,” whose writing is shown here, and whom he describes as “mischievous,” “impish,” and “by all odds the most interesting of the personalities.”

When the American physician Morton Prince met 23-year-old Clara Norton Fowler in early 1898, he concluded he was dealing with a “hysteric.” Fowler, whom Prince referred to by the pseudonym Christine Beauchamp in his notes, was suffering from insomnia, headaches, fatigue, and general agitation. Prince took her on as a patient for treatment by hypnosis.

In a session with her not long after that, however, Prince got the impression that he was speaking with someone else. “This character at first appeared to be a second hypnotic state, but later proved a...

One of the first people to be described as having multiple identities was Louis Vivet (pseudonym: Louis V), a patient studied by various physicians in the late 1800s. French psychologist Pierre Janet wrote of Vivet possessing at least six “existences”—although reexaminations of the case claim that most of these states were induced or created through hypnosis from his therapists. A famous report on Vivet’s case by the writer Frederick Myers was published in 1886, a few months after the publication of Robert Louis Stevenson’s enduring novel about split personalities, Strange Case of Dr Jekyll and Mr Hyde.  

Prince connected Christine’s condition to a similar case described by the French psychologist Pierre Janet and others during the previous decade, and Prince’s book, The Dissociation of a Personality: A Biographical Study in Abnormal Psychology, would become a classic in the literature on multiple personality disorder, now better known as dissociative identity disorder (DID). Characterized as a mental disorder involving two or more distinct personalities—at least one of which usually has partial or complete lack of awareness or memory of other personalities’ thoughts and actions—DID has typically been associated with early-life trauma. But it has always been a controversial diagnosis, from its beginnings in the works of 19th-century psychologists through a boom in interest in the late 20th century to its current disputed status. 

Psychiatrist Joel Paris, who specializes in personality disorders and has criticized what he calls a fad of DID diagnoses in the 1980s and 1990s, credits popular books and films about real-life cases with thrusting the disorder into the public eye—and into the minds of some psychiatrists. In 1957, there was The Three Faces of Eve, a book and then film based on the story of Chris Costner Sizemore, who was diagnosed with the separate, better-known disorder schizophrenia before being told she had multiple personality disorder. “It piqued the public [interest] a lot,” Paris says. Even then, though, psychiatrists were taught “that this thing may exist but it’s extremely rare.” Then came Sybil, a 1976 film based on a book of the same name that told the story of Sybil Dorsett (a pseudonym for Shirley Ardell Mason). After that, Paris says, there was a sharp rise in clinical papers and case reports; some estimates put the incidence of DID at 1 percent of the population. 

Christine “Chris” Costner Sizemore (pseudonym: Evelyn Lancaster) was diagnosed with multiple personality disorder in the 1950s by two psychiatrists who went on to sell the rights to her story to Twentieth Century–Fox. The resulting film, The Three Faces of Eve, led to multiple awards for the actress playing Eve, but Sizemore would later sue the studio after saying she felt that she’d been cheated by the contract that her psychiatrists had arranged.

The concept has long faced pushback from much of the clinical community. The case for DID diagnoses’ legitimacy hasn’t been helped by critical reexaminations of several classic cases, nor by claims that psychiatrists themselves might have inadvertently created or promoted the behaviors they observed in patients. “Some people began to think that maybe these stories concocted were to impress therapists to keep their interest,” Paris says, “or because of direct intervention by therapists who believed in this idea before they even met the patient.”

Psychiatrists have pointed out that Prince's identification of Beauchamp's multiple personalities took place in the context of years of psychological and physical experimentation, and that he made no secret of his preference for Sally, whose “childlike” and “volatile” character was by far the most interesting, in his opinion. In a 2011 book, journalist Debbie Nathan concluded that Sybil, by far the best-known case to date, had invented her condition, plus stories of childhood trauma, to please her psychiatrist, Cornelia B. Wilbur—something Sybil appeared to admit in the 1970s but that Wilbur, by then famous and in the middle of a book project, refused to accept. In the 1990s, a woman in Illinois sued her psychiatrist, the multiple personality disorder expert Bennett Braun, over his alleged role in making her believe, through years of hypnosis and heavy medication, that she developed more than 300 personalities.

Shirley Ardell Mason (pseudonym: Sybil Isabel Dorsett) was the subject of a wildly successful book written by journalist Flora Rheta Schreiber. Later turned into a film, the story is arguably the most famous case of multiple personality disorder. However, a 2011 book alleges, among other things, that Mason’s stories of childhood abuse and multiple personalities were fabricated, that Schreiber knew the story she was writing was untrue, and that Mason’s psychiatrist, Cornelia B. Wilbur, may have knowingly or unknowingly manipulated Mason into medical and psychological dependency on her.

Famous cases aside, some psychiatrists question the plausibility of reports describing people with 10, 20, or more different personalities, at least if the phenomenon is as common as some claim, and argue that cases are diagnosed at just a few institutions loyal to the idea. Proponents of the diagnosis reject these criticisms. A review by prominent DID specialists took on several DID “myths” a few years ago, arguing that the condition is instead underdiagnosed, and is a well-defined and scientifically supported disorder, noting its recognition by The Diagnostic and Statistical Manual of Mental Disorders.

One thing that psychiatrists on both sides of the debate can agree on is that pop culture references to the condition haven’t been particularly helpful—either for understanding the condition or for helping people suffering from mental distress find help. “There are many movies that have used this as a plot device,” says Paris. “This is a world where it’s the story that counts.”

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