Trials of psychedelics for mental health may all be invalid, because everyone knows if they've been given one

Embargoed until: Publicly released: 2026-04-16 01:00

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Drug trials generally involve comparing a treatment with a non-active, placebo version, an approach called 'blinding' because patients must be 'blind' as to which they've received for the trial to work. Canadian researchers say this is a huge issue for studies of psychedelic therapies because it's fairly obvious to patients whether they've been given a psychedelic or a placebo. So, they decided to investigate whether patients were aware of whether they'd been given a psychedelic or a placebo in 112 previous 'gold standard' trials of psilocybin, LSD, ketamine, MDMA, and DMT. They found fewer than one-in-three studies (29.5%) assessed whether blinding had been successful, and blinding failed more than 90% of the time in the studies of psilocybin, LSD and DMT, and 85% of the time in studies of MDMA. The results were better for trials of ketamine, at 17.9%, because a sedative called midazolam can be used as a placebo in trials of that drug. The findings suggest the results of trials of psychedelics for mental health should be taken with a hefty pinch of salt until this problem can be resolved, the authors conclude.