In researching the “real” Emily Rose story, it appears to be another case of blaming the parents and the religion.
The real Emily Rose, Anneliese Michel grew up in a strict Catholic household with three other sisters. Her father once considered the priesthood and three of her aunts became nuns (can’t imagine how fun those family gatherings must have been when no one is getting drunk or telling dirty jokes). But the story is that four years before Anneliese was born, her mother gave birth to a daughter out of wedlock, Martha.
As penance for screwing around outside the marital bed, her mother was forced to wear a black veil on her wedding day. She then forced her daughters to atone for her sins of the flesh through constant prayer. Martha would die at the age of eight and thus caused Anneliese’s mother to dial her prayers up a notch even further. Her mother’s insanity was passed down to her as Anneliese would routinely sleep on bare stone floors to atone for the sins of “wayward priests and drug addicts”.
This script would continue into her college years at the University of Wurzburg when she hung pictures of saints on her door mom walls and scattered holy water around the room. She prayed the Rosary during her ample spare time before slowly going mad or becoming possessed, whichever story you believe.