First Publicly Funded UK Trial of Psilocybin for Treatment-Resistant Depression Publishes Results

Researchers at King’s College London have published results from the first publicly funded randomised controlled trial of psilocybin in the United Kingdom. The trial, known as PsiDeR (Psilocybin in Depression Resistant to Standard Treatments), was funded by the National Institute for Health and Care Research, run in a National Health Service setting, and published in Nature Medicine on 6 August 2026.

What the study reported

According to the university’s announcement and the published paper, 60 adults with treatment-resistant depression were randomly assigned to receive either a single 25 mg dose of psilocybin or an inactive placebo, with psychological support provided to both groups. Neither participants nor researchers were told who received which.

The researchers reported that participants who received psilocybin were, on average, substantially more likely to improve than those who received placebo, with the difference holding at six weeks of follow-up. On the trial’s clinician-rated depression scale, the authors reported a between-group difference of just over ten points at week three in favour of psilocybin. The paper reports that 43 per cent of the psilocybin group met response criteria at three weeks, compared with 3 per cent of the placebo group. Four serious adverse events were recorded across the trial (three in the psilocybin group, one in the placebo group); the authors reported that none were attributed to psilocybin.

Chief investigator Professor James Rucker said people randomised to receive psilocybin “were much more likely to improve than placebo recipients up to 6 weeks follow up.”

Important caveats

The authors themselves are careful about interpretation. Most participants correctly guessed which group they were in — psilocybin’s effects are hard to conceal — and the researchers note that expectation likely accounts for part of the difference, writing that “individual responses were very variable and some difference between groups will be due to non-drug factors.” The trial was also designed primarily to test feasibility, enrolled a modest 60 participants, and followed them for six weeks. These are attributed research findings, not evidence that any treatment works.

The study was independent of commercial sponsors: Compass Pathways supplied the study drug and placebo but, per the paper’s funding statement, had no role in the trial’s design, conduct or analysis.

The Australian picture

Treatment-resistant depression is the one indication for which Australian psychiatrists authorised under the TGA’s Authorised Prescriber scheme may prescribe psilocybin, so independent, publicly funded evidence in exactly this population is directly relevant to the ongoing Australian debate about the strength of the evidence base. The result changes nothing about access: prescribing remains limited to authorised psychiatrists, no psilocybin product is registered on the ARTG, and outside the clinical pathway psilocybin remains illegal to possess or supply in every Australian state and territory.

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