In brief
- A team from the University of Toronto reviewed 112 psychedelic clinical trials to determine if blinding—ensuring participants do not know whether they received the substance or a placebo—holds up in practice.
- In inert-placebo MDMA trials reporting this outcome, correct guesses exceeded 85%; psilocybin, LSD and ayahuasca studies frequently reported values above 90%. This is not a pooled rate for every participant or trial.
- Only 29.5% of the analyzed studies formally measured whether the blind was maintained, despite it being a key factor in interpreting results.
One of the most debated aspects of psychedelic research has finally received a systematic assessment. A team led by Diana K. Orsini at the University of Toronto has published a review of 112 randomized clinical trials in JAMA Psychiatry to answer an uncomfortable question: do participants really not know whether they received the drug or a placebo? The review describes a frequent problem, infrequent assessment and strategies that did not consistently achieve ideal blinding.
What they found
The review covers trials on seven substances: ketamine (78 studies), LSD (17), psilocybin (11), MDMA (11), ayahuasca (2), DMT (2), and noribogaine (1). Of these, only 33—29.5%—formally measured the integrity of the blind, although 64 (57.1%) acknowledged the issue when listing their limitations. When measured, the data were stark: in MDMA trials with an inert placebo, more than 85% of participants correctly identified what they had taken. Psilocybin, LSD and ayahuasca studies frequently reported values above 90% in participants and raters. The abstract does not provide one pooled rate for every person. The abstract states 112 trials, but its listed substance counts sum to 122. Without the complete tables, this review has not resolved whether this reflects overlap or a typographical error; percentages have not been recalculated.
Ketamine and active comparators
Ketamine trials assessed blinding in 17.9% of cases and showed better preservation with midazolam than saline. This does not establish one causal mechanism or make drug effects irrelevant: no strategy consistently achieved ideal blinding. Expectations may bias outcomes without this review quantifying how much of each clinical effect they explain.
What it implies
The review assesses blinding integrity rather than proving all efficacy false or itself deciding regulatory approval. The authors call for standardized measures and designs that distinguish pharmacological effects and expectations; FDA documents or current regulator inventories were not inspected here. For those who follow harm reduction from outside the lab, the reminder remains the same: every headline is backed by an experimental design and margins of uncertainty that are worth understanding. In that same spirit of methodological rigor, we recently published a piece on the MDMA analog without psychedelic effects, as related coverage, without the link resolving this review’s limitations.
Source
- Orsini DK, et al. Blinding Integrity in Psychedelic Randomized Clinical Trials: A Systematic Review. JAMA Psychiatry, July 1, 2026.
Educational content written from a harm reduction perspective and with respect for individual freedom. It is not a substitute for advice from a healthcare professional and is not intended to encourage or condemn any drug use.
