However, the film's screenwriter, William Peter Blatty, claimed to have been inspired by the 1949 case of "Roland Doe" (a pseudonym used to protect the boy's identity), which was documented in the book "The Exorcism of Emily Rose" by Thomas B. Allen.
Here's what we know about the Roland Doe case:
* The boy, whose real identity remains unknown, was a 13-year-old boy who lived in Cottage City, Maryland, in the 1940s. He experienced unusual, disturbing behavior, including violent outbursts, speaking in tongues, and levitating.
* The boy's family sought help from Catholic priests, who eventually performed an exorcism ritual. The exorcism reportedly lasted several days and was witnessed by several people.
* The boy eventually returned to a normal life and lived a long life.
* The case was documented in the book "The Exorcism of Emily Rose" (2000), which served as the inspiration for the 2005 film of the same name.
It's important to note:
* The Roland Doe case is a complex and controversial one. While some believe it was a genuine case of demonic possession, others attribute the boy's behavior to mental illness or even a hoax.
* There is no concrete evidence to support the claims of demonic possession in the Roland Doe case. The accounts rely heavily on anecdotal evidence and personal testimonies.
* The film "The Exorcist" takes significant creative liberties with the Roland Doe case. While it draws inspiration from the events, it is primarily a fictionalized reimagining of the story.
Therefore, while "The Exorcist" is not based on a single true story, it is inspired by the Roland Doe case, which serves as a starting point for the film's exploration of the themes of demonic possession and the battle between good and evil.