The same could be said for a lot of drugs that have strong side effects, just one difference here is the main "side effects" are something some people consider

The same could be said for a lot of drugs that have strong side effects, just one difference here is the main "side effects" are something some people consider fun. Though you could still do double-blind for comparing the effectiveness of different psychedelics, e.g comparing LSD to Psilocybin.