Crazy as Hell

Crazy as Hell, released in 2002 New York and L.A. only, is a horror suspense film that is based on the 1982 novel Satan, His Psychotherapy and Cure by the Unfortunate Dr. Kassler, J.S.P.S. by Jeremy Leven and follows Dr. Ty Adams Michael Beach, an aggressive and overconfident psychiatrist producing a documentary film about a nearby staterun mental hospital. While treating a new patient Eriq La Salle, who also directed who claims to be Satan, Dr. Adams begins to question his own perceptions.

Source: Wikipedia