Requiem for a Dream was one of the first movies I ever watched about drugs before I ever started doing drugs, and I actually just recently rewatched it for the first time in a very long time.
I was in my teens and still had a sort of innocence about me at that time any while understanding that it was about drugs I didn't understand the depth and breadth of the conveyed message in it about drug use.
In rewatching it I noticed something a friend of mine pointed out some years ago:
In the ending, the only one that got what they wanted out of it was the girl, she just had to pay a dehumanizing price for it. Which in of its own is a commentary that is meant to prompt the same question that the others stories all prompt: "Is it worth that much to you?"
The film does have an amazing soundtrack, I will definitely give it that, and yes, a lot of the stuff that happens in it, if you are not careful and use proper caution that stuff can in fact happen when you become that addicted. I've known people who've seen that side of it, unfortunately.
When I was younger I did not understand a lot of what I was seeing other than I found it visually disturbing at the time...not so much anymore though.
There is also a factor that it's a film that is subject to its time period and even then it takes place probably a decade or so before its time period in terms of the plot. Back then, people didn't really have the internet and home computers like how they do now, so you had to know a guy who knows a guy for pretty much everything, not just drugs but also even if you fucked yourself up while using as well or ended up having any kind of issues with your connect, etc.
But thankfully we now live in a world where resources and harm reduction are much more at the fingertips of people to help reduce such tragedies.
I do love the movie though. I just rarely watch it due to its take on the subject matter.