Schism(2008)

Linda has a multiple personality disorder. She hosts a talk show called In Touch With Insanity. The idea behind the show is that insane people should have the right to express themselves, regardless of what society thinks of them. Viewers call in and speak to Linda's various personalities about their own insanity and how they live with it. If they need help she refers them to the doctor who is treating her. Unbeknownst to Linda, viewers of her show are being murdered. Is the murderer a psychopathic viewer? The doctors? Or one of Linda's own personalities?