In brief
- PsiDeR, the first randomized psilocybin trial funded by public money in the UK and conducted within the National Health Service (NHS), has published its results in Nature Medicine.
- Out of 60 people with treatment-resistant depression, 50% of those who received 25 mg of psilocybin responded to treatment at six weeks, compared to 3% in the placebo group.
- The research team itself notes that blinding failed: the entire psilocybin group and 70% of the placebo group correctly guessed which treatment they had received.
Until now, almost all solid evidence regarding psilocybin and depression came from trials funded by companies with a direct commercial interest in the outcome. That has just changed: the PsiDeR trial, funded by the UK’s National Institute for Health and Care Research (NIHR) and conducted entirely within the NHS, has published the first data from a publicly funded randomized psilocybin study in Nature Medicine.
A small trial with careful design
The team, led by psychiatrist James Rucker from the Institute of Psychiatry, Psychology & Neuroscience at King’s College London, recruited 60 people with treatment-resistant depression—meaning they had already tried at least two antidepressants without success. Half received a 25 mg dose of psilocybin with psychological support during the session; the other half received a true placebo—not an active microdose, the method that has compromised the blinding of other trials—and the same support. The entire process took place in NHS facilities, a first for this type of research in the UK.
Half responded, and improvement was maintained
At three weeks, 43% of the psilocybin group showed a clinically relevant response; at six weeks, this rose to 50%. In the placebo group, the figure remained at 3% at both intervals. Complete remission of symptoms reached 40% in the psilocybin group at three weeks and was maintained at six, compared to 3% for the placebo. A total of 287 adverse events were recorded (164 in the psilocybin group and 123 in the placebo group), most of which were mild, along with four serious adverse events—three in the psilocybin group and one in the placebo group—none of which were ultimately attributed to the compound.
What this implies
The most interesting aspect of this work is its methodological honesty. The researchers acknowledge that all participants who received psilocybin and 70% of those who received the placebo correctly guessed their assignment, concluding that “expectancy, and not just pharmacology,” likely explains part of the difference between the groups. It is the same underlying problem we have discussed on other occasions: with substances that have noticeable effects, the classic double-blind is an awkward fiction that research has yet to resolve.
Furthermore, this is a small sample of 60 people with results at six weeks: nothing that allows us to speak of a consolidated therapy. Its value lies elsewhere. It is the first time a European public health system has invested its own money and structure to verify, without a commercial sponsor involved, whether psychedelic-assisted therapy works under real-world healthcare conditions. And that kind of evidence, generated outside the circuit of pharmaceutical companies that already have phase 3 trials underway, is precisely what carries the most weight when a public service decides what to fund and what not to.
Source
- King’s College London. Promising results from first publicly funded UK randomised trial of psilocybin for depression. King’s College London, regarding the PsiDeR study published in Nature Medicine, August 6, 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.
