I saw this movie a couple years ago and I forget the title... ?

Alright, I saw this movie a couple of years ago and I can't remember what it is called. I don't remember a lot about it, but I do remember there was this woman who is a therapist in a mental institution and there is a man there who is insane, but at the end, like the last five minutes, she is sitting on a chair bald and you find out she is actually a patient at the institution and she was being studied at a university and the guy is the professor. That is what I remember, but it may not all be right. I remember I thought it was good though and I would like to see it again. Do you have any idea what it is?