Open-label trial · 2026
A second group psilocybin session for cancer patients who only partly improved the first time
- Original title
- A phase 1 study of a second experience with Group Retreat Psilocybin Therapy for partial responders after a first experience.
- Authors
- Back AL, McGregor BA, Thorn LL, et al.
- Journal
- Frontiers in public health, 2026
- Molecules
- Psilocybin
- Conditions
- Depression, Anxiety, End-of-life distress
- Participants
- 13
- Evidence grade
- Very low
- Source
- Read the original paper
The question
Is it safe and workable to offer a second group psilocybin session to people with metastatic cancer who only partly improved after a first session?
What they did
Thirteen adults with metastatic cancer who were partial responders in an earlier group psilocybin study took part in a second retreat. Average age was 56, 70% were women, and 38% were taking antidepressants, which they were not required to stop this time. The starting dose was raised to 35 mg, with an optional 10 mg booster for people who reported little effect at 60-90 minutes and passed a safety check. The retreat included three preparation sessions, one dosing day in a group format with four main facilitators, and four integration sessions.
What they found
No serious adverse events occurred. Mild effects included temporary raised blood pressure (4 people), nausea (3) and headache (1). Seven participants (54%) took the booster dose. Average scores on the Hospital Anxiety and Depression Scale fell from 15.08 at baseline to 9.00 eight days later, and were 10.42 at 24 weeks; 69% scored below the clinical cut-off. The share of participants reporting a “complete” mystical experience rose from 38% in the first session to 77% in the second, without more difficult experiences, and ratings of social support and group cohesion improved through 24 weeks.
The fine print
This was a small safety study with 13 people, no comparison group and no placebo, so improvements could reflect expectation, extra group support, or natural change over time. Everyone had already chosen to return for a second session, which selects for people who found the first one acceptable. Several things changed at once — higher dose, optional booster, no antidepressant tapering — so the effect of any single change cannot be separated. This summary is based on the abstract only.
What it means
In a small group of people with metastatic cancer, a repeat group psilocybin session was delivered without serious safety problems and was followed by lower anxiety and depression scores, but the design cannot show that the psilocybin caused the improvement.
Evidence grade: Very low. A single-arm Phase 1 safety study in only 13 people, with no control group and no blinding, so the mood changes cannot be attributed to psilocybin with confidence.
This summary is based on the study’s published abstract.