In brief
- PsiDeR is a randomized feasibility trial at one NHS site in England, with NIHR funding and product/placebo supplied by Compass; it does not establish routine clinical availability. The paper was published 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.
- Blinding was assessed in 23 participants: 13 of 13 psilocybin recipients and seven of ten placebo recipients guessed correctly; this was not assessed in the whole sample.
PsiDeR, funded by NIHR and academically sponsored by South London and Maudsley NHS Foundation Trust and King’s College London, assessed randomized-trial feasibility within the NHS. Compass supplied product and placebo and, according to the paper, had no role in design, conduct or analysis. Public funding alone does not establish greater evidential weight or absence of interests. Results were published in Nature Medicine.
A small feasibility trial
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—with inadequate response to two antidepressants or one plus a psychotherapy, under the paper’s eligibility criteria. Half received a 25 mg dose of psilocybin with psychological support during the session; the other half received an inert placebo without psilocybin and the same support. The trial moved from an NHS clinical research facility to a community setting. The authors describe it, to their knowledge, as the first feasibility trial in that English setting using an inert placebo; this is not an inventory of all European publicly funded research.
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. The MADRS remission threshold of ten or less was reached by 40% in the psilocybin group at three weeks and was maintained at six, compared to 3% for the placebo. The randomized phase recorded 287 nonserious events: 164 in psilocybin and 123 in placebo. Four serious events spanned both phases, three during the open extension and one during the randomized phase; by original assignment, three were in psilocybin and one in placebo. Events in psilocybin recipients were judged unrelated; the placebo-arm event was considered possibly related to study medication. This classification does not establish general absence of risk.
What this implies
The most interesting aspect of this work is its methodological honesty. Among the 23 participants asked, 13 of 13 in psilocybin and seven of ten in placebo guessed correctly; the authors suggest that expectancy, alongside pharmacology, may explain part of the difference between the groups. It is the same underlying problem we have discussed on other occasions: functional unblinding limits interpretation without itself nullifying the design or quantifying each factor’s contribution.
This is a small feasibility study with six-week randomized follow-up, not confirmation of long-term efficacy or cost-effectiveness. Delivery within a public service contributes experience on evaluating psychedelic-assisted therapy in that setting, with further evidence needed before access or funding decisions. The entire evidence base cannot be ranked solely by funding source.
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.
