You don't need to be creative to sing or play. You need to be creative to compose.

Do we actually know that many creative musicians, writers etc. were creative before using? I'd imagine it's really tricky to track down the starting dates of drug use. Or when someone started composing for that matter.

But yeah, that was just to illustrate the point anyhow. And the point is that people self select heavily on which drugs they use. So the user group of any drug is not representative sample.