In the early 1950s, Mason moved to New York City to pursue graduate studies at Columbia University. Plagued by blackouts and breakdowns for many years, she began seeing a psychiatrist, Dr. Cornelia Wilbur, who eventually diagnosed Mason with Multiple Personality Disorder. Wilbur discovered 16 different personalities within Mason and believed they were a result of severe child abuse. During 11 years of therapy, Wilbur and Mason worked to integrate these personalities into one complete self, and afterwards Mason found she was content and well adjusted.

In 1973, journalist Flora Rheta Schreiber wrote Mason's story with input from both Mason and Wilbur. In the book, Mason's name was changed to Sybil Dorsett to protect her privacy. The book Sybil was hugely popular and was made into a TV movie in 1976 starring Sally Field. Field won an Emmy for her performance, and the story of Sybil deeply influenced both pop culture and the mental health profession.

After the book was published, Mason moved to Lexington, Kentucky. Wilbur taught at the University of Kentucky, and the two remained close friends for the rest of their lives. Mason was an art teacher and a prolific painter. She lived a quiet life in Kentucky, going to a Seventh Day Adventist church, taking care of her pet poodles and cats, and playing Scrabble with Wilbur and a few close friends. She never married or had children. In 1998, Mason died of breast cancer at the age of 75, and it was not until after her death that she was publicly revealed as "Sybil."

In recent years, doctors and other pundits have debated whether or not Multiple Personality Disorder (now known as Disassociative Identity Disorder) really exists. Some claim that Mason's 16 personalities were created by Wilbur's suggestions during therapy. Both Mason and Wilbur are deceased (Wilbur died in 1992), so we may never know more about this unusual story. http://ask.yahoo.com/20020502.html