There is no way to placebo control a psychedelic really, as that effect is easily discerned, even in a closed label trial. Therefore, a comparison protocol is u

There is no way to placebo control a psychedelic really, as that effect is easily discerned, even in a closed label trial. Therefore, a comparison protocol is used instead, which is anyway superior to pure placebo control. A different psychedelic, which is not expected to have an antidepressant effect, or a low, psychoactive but not antidepressant dose. Or known non-psychedelic antidepressants which have been placebo tested.