As retold in this latest video documentary from Retro Report, part of a series exploring past news stories and their consequences, the phenomenon burned most intensely for roughly a decade, from the mid-1980s to the mid-'90s. Then it faded from public view, partly the result of lawsuits brought successfully against some psychiatrists, who were found by the courts to have used dubious methods to lead their patients down the path of false memories.

When an unusual disorder draws so much attention, as this one did for a time, the public may become understandably confused about how prevalent it truly is. Even with medical conditions that are less controversial and far more familiar to most Americans, questions arise. Consider a developmental disorder like autism or Asperger syndrome. A federally supported study in 2013 found that the likelihood of a school-age child’s receiving such a diagnosis had risen 72 percent in just five years. Cases of attention deficit hyperactivity disorder have increased so starkly that it is now said to affect, at some point, 11 percent of Americans from ages 4 to 17. In 2007, researchers reported a 40-fold increase in the number of children and adolescents being treated for bipolar disorder. Do these striking statistics signal that the disorders are indeed increasing explosively, or have doctors simply gotten better at recognizing existing problems? Or, less reassuringly, are some of these conditions perhaps being overdiagnosed? Medical professionals themselves continue to debate such questions.

The “Sybil” story began in the mid-1950s. At its center were the Minnesota-born Ms. Mason and her intense relationship, first in the Midwest and later in New York, with a psychoanalyst, Cornelia B. Wilbur. Dr. Wilbur’s determination that Ms. Mason had 16 personalities — people of varying manner and ages, including two who were male — did not come about in a vacuum. She was well aware of “The Three Faces of Eve,” a 1954 report by two psychiatrists who worked with a woman said to have had three distinct personalities. (As Eve in a 1957 film based on that study, Joanne Woodward won an Academy Award for best actress. Years later, she did a neat Hollywood pivot by playing the psychiatrist in the first movie version of “Sybil,” with Sally Field as the patient.)

Dr. Wilbur did not write up her findings in some dry professional journal. Instead, she went looking for a large audience, and enlisted a writer, Flora Rheta Schreiber, to produce what became a blockbuster. But as the years passed, challengers began to speak up. One was Herbert Spiegel, a New York psychiatrist who said that he had treated Ms. Mason when Dr. Wilbur was on vacation. Dr. Spiegel described his patient not as a sufferer of multiple personality disorder but, rather, as a readily suggestible “hysteric.” A harsher judgment was rendered in the 1990s by Robert Rieber, a psychologist at John Jay College of Criminal Justice, a New York City school where Ms. Schreiber taught English. After listening to tape recordings that he said Ms. Schreiber had given him, he concluded that “it is clear from Wilbur’s own words that she was not exploring the truth but rather planting the truth as she wanted it to be.” Debbie Nathan, a writer interviewed for this Retro Report documentary, piled on still more skepticism in her 2011 book, “Sybil Exposed.” Perhaps inevitably in a dispute of this sort, counter-revisionists then emerged to denounce the doubters and to defend “Sybil” as rooted in reality.

Overwhelmingly, those receiving a diagnosis of the disorder have been women. They typically had rough childhoods. A pattern to their stories — Ms. Mason fell squarely within it — was that they endured horrific physical and sexual abuse when they were little. More than a few claimed to have been the victims of torture at the hands of satanic cults. In many cases, their memories were brought to the surface through hypnotism or with injections of so-called truth serums like sodium pentothal. But were those recollections real? The “Sybil” phenomenon went arm in arm with a reassessment of certain psychiatric techniques. Some studies concluded that people may have become less inhibited with pharmacological intervention, but not necessarily more truthful. Other research found that hypnosis sometimes creates false memories. Those who dismiss Dr. Wilbur’s work as hokum say that induced false memories lay at the heart of her work with Ms. Mason.