

Mason was a devout Seventh-day Adventist.

The following year, Wilbur developed Parkinson's disease, and Mason moved into Wilbur's house to take care of her until Wilbur's death in 1992. Wilbur diagnosed Mason with breast cancer in 1990, and she declined treatment it later went into remission. She taught art classes at a community college and ran an art gallery out of her home for many years. She later moved to Lexington, Kentucky, where she lived near Wilbur.

By that time, Mason had severed nearly all ties with her past and was living in West Virginia. Some people in Mason's hometown, reading the book, recognized Mason as Sybil. From 1970–71, she taught art at Rio Grande College in Rio Grande, Ohio (now the University of Rio Grande). Their sessions together are the basis for Flora Schreiber's book on Shirley Mason. She had long suffered from blackouts and emotional breakdowns, and finally entered psychotherapy with Cornelia B. In the early 1950s, she was a substitute teacher and a student at Columbia University. Shirley Mason graduated from Dodge Center High School in 1942 and became an art student at Mankato State College, now Minnesota State University, Mankato. At one point, Martha Mason was reportedly diagnosed with schizophrenia. She didn't laugh much, but when she did, it was like a screech." Christensen remembers Mason's mother walking around after dark, looking in the neighbors' windows.

In regard to Mason's mother: ".many people in Dodge Center say Mattie" - "Hattie" in the book - "was bizarre," according to Bettie Borst Christensen, who grew up across the street. Shirley Mason was born and raised in Dodge Center, Minnesota, the only surviving child of Walter Wingfield Mason (a carpenter and architect) and Martha Alice "Mattie" Atkinson. Mason herself eventually told her doctor that she did not have multiple personalities and that the symptoms had not been genuine, although whether or not this statement accurately reflected Mason’s views later in life remains controversial. Wilbur have been criticized, with allegations that Wilbur manipulated or misdiagnosed Mason. Mason's diagnosis and treatment under Cornelia B. Both the book and the films used the name Sybil Isabel Dorsett to protect Mason's identity, though the 2007 remake stated Mason's name at its conclusion. Two films of the same name were made, one released in 1976 and the other in 2007. Her life was purportedly described, with adaptations to protect her anonymity, in 1973 in the book Sybil, subtitled The True Story of a Woman Possessed by 16 Separate Personalities. Shirley Ardell Mason (Janu– February 26, 1998) was an American art teacher who was reported to have dissociative identity disorder (previously known as multiple personality disorder).
