> Traditional antidepressants take days or weeks to have an effect, and the effect is very different from psilocybin.
Which is fine. Double-blind is great when you can pull it off, but it's fallacious to dismiss control groups just because they can't be perfectly blinded.
Active control groups and non-blinded studies are still used frequently in these situations. There's no excuse for discarding control groups completely.
Traditional antidepressants take days or weeks to have an effect, and the effect is very different from psilocybin.
>So they could have simply had one group receive only therapy and the other group receive therapy plus psilocybin.
That still wouldn't tell you if the psilocybin itself had any effect over and above the placebo effect.