Interestingly, while chatting with the AME during my last renewal, she mentioned nonchalantly that a high percentage (I didn't ask how much exactly) of tests come up positive, with marijuana being the favourite amongst PPLs, and cocaine amongst CPLs.
This kind of took me aback, as I thought it would be the other way around, with affluent people who can afford to fly privately taking the more expensive drugs, while the skint, overexploited, debt-laden professional would have to make do on the cheap stuff.
She didn't mention what the consequences of a positive result were so I can't help there, but since we were talking renewals, it's fairly obvious that illicit drug consumption amongst pilots is all but unheard of.
On the good news front for all of you druggies out there: a) they don't seem to check for
glue sniffing (and neither for typewriter correcting fluid, for the white-collar amongst you), and b) alcohol and caffeine are socially accepted anyway, so hopefully you now know what to stick with.