Personally, I haven't witness any drug use in the various developer circles I've run except for ADHD meds. The number on ADHD meds is somewhere around 5-10% I would guess...
There's strong selection bias with drug use because drug users tend to cluster together, I suspect it's a lot less common than people think.
Demand is not what the weed industry thought it would be.[1]
[1] https://www.foodengineeringmag.com/articles/99944-price-per-...