Movies about medical patients and the supernatural

I agree. What also really worked for me was the building on our already established fears of Alzheimer's. If you've ever seen someone go through that disease, it is utterly frightening - the person sees people who aren't there, talks to people who aren't there, often speaks in strange voices, act in ways that are unlike themselves, etc. It's really scary and can seem paranormal, or at least give you a creepy feeling of something paranormal happening. I really liked how they started with Alzheimer's. It gave the film a scary, unsettling vibe from the get go.

I respectfully disagree with the stigmatising bit, as I believe that there already is a stigma on mental diseases. I do not believe the films make it worse, as it is fiction. I actually wonder if it doesn't highlight the differences.
Besides, a lot of witch hunt victims in the past were mentally disabled people and a mental imbalance would make a possession easier.
Also, a movie about a haunting or a possession where people disregard the medical possibilities gives me scary 'what if' feelings about the protagonists.
I'm actually still looking for a good possession and/or haunting film that takes place at least partly in an asylum (I adore Gothika).