I like to call it psilo-cebo for mushrooms, or psyche-cebo in general.

The approach should be to use different types of psychoactive drugs to multiple pseudocontrol groups. Have a control group have placebo, then another LSD, another Ketamine, another a synthetic cannabinoid, another mushrooms.

That way even if the effects are genuine of psilocybin it will pop from the rest in the results, if is in psychedelics in general LSD will pop as well, if it's anything "mind exploring" Ketamine will pop too, if it's just getting high what makes things better, the cannabinoid will join into the results.

And obviously this has to be done on people without drug experience, because the effects are rather easy to tell apart by drug users.