Leonardo DiCaprio says being alone is his "personal demon".
The 35-year-old actor admits he struggles to cope when he is not surrounded by his friends and family and suffered from depression when he shot latest movie 'Shutter Island'.
He said: "The loneliness is my personal demon. During the shooting of the movie it was like I fell into a black hole and was totally depressed.
"You're cut off from friends, family - and your girlfriend. That's brutal. The world kept turning while I was stuck on the set. It's like a strange form of everyday amnesia."
The movie is directed by Martin Scorsese and Leonardo admits he has became like a father to him after working together on several movies including 'Gangs of New York' and 'The Departed'.
He told TV movie magazine: "We share a special relationship. Martin trusts my instincts.
"He is also Italian, from the same neighbourhood and at the same age as my father. He gives me as an actor always the feeling of security."