"The Myth is Everything" - Sergio Leone

DC, I'm not the biggest fan of the opium theory, but consider this:

For centuries, people of culture around the world considered mind-altering narcotics to be a "key" of sorts to going outside the body and exploring the universe, through time and space. Marijuana, LSD, and especially Opium were such tools for such "voyages."

Warning, Spoiler:
The movie's opening dictates two hitmen looking for Noodles to whack him, but we forget about them after they rough up Noodles' girl. But we return at the end, Deniro back at the age of the movie's opening...stoned out by opium. Did Noodles have a view to a possible future that he may never have now that the hitmen are on their way to eliminate him? A little JACOB'S LADDER, eh?