The film is based on the 2003 novel by Dennis Lehane. It follows the investigation of the disappearance of a criminally insane patient from a hospital on an island in Massachusetts.
DiCaprio told Parade: "I have to say Shutter Island was one of the most intense, hardcore filming experiences I’ve ever had as we explored what the mentally ill had to face in the days when mental hospitals were called insane asylums. It was really very traumatic, and I don’t say that about a film very often. I went to places and unearthed some things that I didn’t think I was capable of.”
The actor has also claimed that during production he had "bloodcurdling nightmares of murder" but gets his therapy from relaxing with his friends.
Shutter Island, also starring Ben Kingsley and Michelle Williams, will release nationally on February 19.