> after he smoked his ambition to be a goos drummer away.

This is the part that doesn't follow. We have no actual indication that smoking pot had anything to do with his lack/loss of ambition.

I could give plenty of anecdotal studies where people became complacent because they got a promotion, or made it to a certain landmark, or realized that they were the smartest person in the room at the time, or a million other things. Complacency is not something that requires smoking pot to feel.

Like, I don't want to denigrate the person in the anecdote - but if your sense of identity is so tied up in being the best drummer among a certain peer group that when you lose that title you are going to attempt suicide, you have more fundamental psychological problems to deal with.

If pot was causing people to want to kill themselves because they weren't the best at something, we'd have a lot more suicides in the world. It's a massive claim, and one that requires proof beyond an anecdote.

“ This is the part that doesn't follow.”

This is what follows, or at least strongly implied, from OP’s post;

“ My friend spent the whole year smoking marijuana and being complacent”

We can only argue from what is in the story. Not what is not in it or what we’d rather wasn’t.

The OP shared a story, admitting its anecdotal.

When someone who retreats from their hobbies, tries to kill themself, and engages in risky behavior like heroine use and drug use, I think its reasonable to suspect that person has some problems in their life beyond smoking marijuana.