Blinding integrity in psychedelic research: Evidence from a comparative randomized controlled trial of psilocybin, MDMA, and methylphenidate in healthy volunteers

Published May 28, 2026European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology

How well people stay unaware of treatment type in studies comparing psilocybin, MDMA, and methylphenidate in healthy volunteers

AI simplified

Psychedelic Science on OpenScience ↗PubMed ↗DOI ↗

Page updated May 30, 2026

Abstract

Overall blinding was found to be insufficient in a study involving 120 healthy volunteers receiving psilocybin, MDMA, or methylphenidate.

Psilocybin exhibited the highest rates of functional unblinding compared to MDMA and methylphenidate.
Methylphenidate, acting as an active placebo, maintained more effective blinding for MDMA than for psilocybin.
Incorporating certainty levels in substance guesses resulted in lower rates of functional unblinding.
Decision factors and subjective experiences were linked to the phenomenological effects of the substances.
Prior experiences with substances did not affect the accuracy of participants' forced-choice guesses.

AI simplified

Maintaining effective blinding is a major methodological challenge in psychedelic research. This study provides a comprehensive evaluation of blinding integrity in 120 healthy volunteers who received either psilocybin, MDMA, or methylphenidate (active placebo) in a double-blind, randomized controlled trial. Using a multi-level assessment incorporating forced-choice substance guesses, certainty ratings, decision factors, and subjective substance effects, the analyses characterize blinding integrity and its relation to the substance experience. Results indicate that overall blinding was insufficient, with psilocybin showing the highest rates of functional unblinding, MDMA moderate levels, and methylphenidate the lowest. As an active placebo, methylphenidate provided more effective blinding for MDMA than for psilocybin. Incorporating certainty levels of substance guesses revealed a more differentiated pattern, with lower functional unblinding rates. Decision factors and subjective substance experiences were associated with phenomenological substance effects. Prior substance experiences did not influence accuracy of forced-choice substance guesses. These findings provide empirical guidance for the design and reporting of blinding procedures in psychedelic trials and underscore the value of systematic, multi-level assessment of blinding integrity.