Editing Shutter Island 'was difficult'
Based on the 2003 mystery novel by Dennis Lehane, the film tells the story of US marshal Teddy Daniels who is investigating the disappearance of a murderess who escaped from a hospital for the criminally insane.
Titanic and Blood Diamond actor Leonardo DiCaprio takes on the role of Daniels, while Mark Ruffalo and Ben Kingsley also star.
Speaking to the Scotsman, Scorsese said Shutter Island was a difficult film to edit.
The Departed director said: "With the editing we found that just putting in one reaction shot could throw the scene off completely."
He added that most of the movie was filmed in an abandoned mental institution in Medfield, Massachusetts, which had "the feeling of a trap, a labyrinth a labyrinth of the mind, which is what I wanted."
The film will be released in the UK on March 12th.