Shock Corridor

Shock Corridor is a 1963 film, directed and written by Samuel Fuller. The film tells the story of a journalist who gets himself committed to a mental hospital in order to track an unsolved murder. Fuller originally wrote the film under the title Straitjacket for Fritz Lang in the late 1940s, but Lang wanted to change the lead character to a woman so Joan Bennett could play the role.

The three witnesses to the murder were driven insane by the stresses of war, bigotry or fear of nuclear annihilation.After a hospital riot, Barrett is straitjacketed and subjected to shock treatment. Barrett begins imagining that his girlfriend really is his sister, and experiences many other symptoms of mental breakdown. He learns the identity of the killer and violently extracts a confession from him in front of witnesses and writes his story. His mind is crucially damaged, however, and he has to stay in the hospital for an undefined period of time. ........

Source: Wikipedia