Abstract

Psychedelics such as psilocybin reliably produce significantly altered states of consciousness with a variety of subjectively experienced effects. These include certain changes to perception, cognition, and affect,1 which we refer to here as the acute subjective effects of psychedelics. In recent years, psychedelics such as psilocybin have also shown considerable promise as therapeutic agents when combined with talk therapy, for example, in the treatment of major depression or substance use disorder.2 However, it is currently unclear whether the aforementioned acute subjective effects are necessary to bring about the observed therapeutic effects of psilocybin and other psychedelics. This uncertainty has sparked a lively—though still largely hypothetical—debate on whether psychedelics without subjective effects (“nonsubjective psychedelics” or “non-hallucinogenic psychedelics”) could still have the same therapeutic impact, or whether the acute subjective effects are in fact necessary for this impact to be fully realized.3,4,5.