20 Things You Didn't Know About Shutter Island

2. Scorsese Worked With A "Psychiatric Adviser" During Production

In order to ensure psychological authenticity throughout shooting, Scorsese worked with a "psychiatric adviser" during production, Professor James Gilligan of New York University.

Though Scorsese and DiCaprio have both remained vague about the precise meaning of the film's ambiguous final moments where Laeddis is led away to be lobotomised, Gilligan freely offered up his own assessment of the story.

Gilligan supports the theory that Laeddis had become aware of murdering his own wife and failing to protect his children, and so willingly pretended to regress in order to be lobotomised, therefore sparing himself the truth of what he'd done.

While you can argue that Gilligan is just another voice opining on the film, considering that he was Scorsese's go-to during filming, he's the closest we've got a definitive "word of God."