>New study finds psilocybin greatly and quickly relieves depression Nope, it doesn't. The study wasn't placebo controlled. The placebo effect will have a large effect in a study like this, so we have no idea what effect the psilocybin had.
What kind of placebo could you use to stand in for a treatment that normally has immediate and obvious side effects like this one?
They could have used an active control group that received traditional antidepressants.
This study wasn't actually about psilocybin, it was about psilocybin-assisted therapy. So they could have simply had one group receive only therapy and the other group receive therapy plus psilocybin.