Wir Kinder vom Bahnhof Zoo? (I think the Engish title was Christiane F.)
Correct, Laura Hunt! Great german movie with David Bowie soundtrack!
Ah rats... all I could think of was "Christine", but knew that wasn't it... 
If it's that one, then I watched it around same age as TheFrighter, maybe a year older, but not much more. I agree, not exactly age appropriate, but it sure made sure that I never ever had any interest in drugs after watching it. 
lol, it's pretty hardcore indeed for a 13 y/o

I watched in early '80s in italian tv, when the "parental control" thing was far to come and every kind movies passed at evening without restrictions... other ages. The effect of a so crude movie on my childhood mind? I'm not a twisted person (well, I hope so) and I totally hate drugs.
This movie is sure the best againist drugs that many others "just say no" stuff.
_