Seriously, though, back in the day, they used to do exorcisms and things (and I think they still do, in some parts of the world), and I always thought that that was just a holdover from more primeval times, where they didn't understand the concepts of mental illness and seizures and things like that, and they were trying their best to understand it through the limited knowledge they had as evil spirits and demons taking control of someone's body and making them say and do irrational, disturbing things...
...But now, a part of me's thinking, "And who's to say they were wrong?"