[NobleFree]

Will a lot of them move up the ladder to drugs that kill or incapacitate them?

No - almost half of Americans have used pot, and most never move up the ladder.

[rhombus10]

almost half of Americans have used pot, and most never move up the ladder.

No one you know, perhaps. I've known bank vice presidents, engineers, software designers and defense workers... I'm retired now, and I've known these smokers for a long time. None of them had trouble moving up any kind of ladder they wanted to... your experience might differ but that's mine.