During the middle ages, as well as at other times, mentally ill people were sometimes forced to undergo the religious ritual called exorcism. this was in order to

"Cleanse them"
People with mental illness in that age often were seen as crazy if they talked about it and if they did't they would become crazy in that time period people believe insanity or really anything that made people differnet was a sign that satan had a hold of them and so since they were wrong most people ended up dying or being a outcast the rest of there life.