The cast and crew of the film underwent a complicated filming and full of problems. And some of the misfortunes would accompany those who were involved in the production even after the filming was completed:
A fire destroyed the Decorated
The filming date had to be delayed because a fire destroyed the decor of the MacNeil house. The director blamed an animal, probably a bird that makes its way through the circuit boxes that caused the fire. The chilling detail is that the whole place was unusable, except Regan's room, which remained intact in the flames.
Real screams of pain
Both Linda Blair, the famous Regan and the actress who played her mother, Ellen Burstyn, suffered severe damage to the back when they performed risky scenes in which their characters were shaken and thrown around the room. In one of the shots, which still remains in the movie, Regan throws her mother by, at that time, Burstyn's backbone was damaged (it's forever) and the actress's screams in the movie are real, pure pain.
Unorthodox methods
Some of the methods used during filming may increase the general perception of morbidity. On the one hand, Friedkin's methods were far from orthodox. Before filming a scene, the director suddenly hit actor Father O'Malley to get the expression he wanted. At another time, he shot with a real gun right behind Jason Miller to get a realistic interpretation of the impact and fear of Father Karras. As for the postproduction, for the scene where the devil finally leaves the body of Regan were recorded several sounds, one of them was the one of several pigs shouting in the slaughterhouse
Family Tragedies
Linda Blair's grandfather and Max Von Sydow's brother, who also died the first day of filming. And although he escaped, Jason Miller's son was about to die from a motorcycle coup. In 1987, actress Mercedes McCambridge, who made the voice of the demon Pazuzu, lived a new tragedy when her son murdered his wife and children before committing suicide.
Side effects
During the passes, people would faint, vomit, and somatizaban the discomfort that their visionado produced them. A woman came to sue Warner Brothers because she claimed that the subliminal messages made her feel so terrified that when she left the theater she stumbled, breaking her jaw. Also, during the rest of the 70 was blamed to have caused a great amount of suicides of people who could not have assimilated what they saw.
By: http://www.elmundo.es/f5/2016/09/23/57e4283e468aebd9278b458c.html