Here's a small detail that seems to have slipped everyone's radar. Like many Metal Gear Solid games, the Phantom Pain lets you smoke. Only this time, the game says that the cigar contains a "medicinal herb".
While this "medicinal herb" could be just about anything, The Game Theorists argue that the fact the herb alters your perception of time makes it very likely that what the game references is actually pot. Funnily enough, the first time Metal Gear Solid gave players cigarettes, the only time they were actually useful were in the last portion of the game, when the facility you're in is about to self-destruct. If you equip the "cigarettes" then, they mysteriously grant you more time to get out of the facility. They, in essence, slow down time. Hmm!
Has Snake been a pothead this entire time? That'd be hilarious.