Just an anecdote of mine. I'm sure there was plenty of drug use in other provinces but my personal experience was in the Helmand. I try not to talk about other places and units I don't have experience in.
Was their a lot of drug use going on? Which drugs?
Oh yea. Mostly weed and some opium. In my company over 50% of us smoked weed.
Lots of Afghanis use opium. Not much else to do out there.