Two psilocybin sessions and depression: what the Johns Hopkins trial found
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The question
Earlier psilocybin studies had looked at people with cancer-related distress or depression that had not responded to other treatments. A team at Johns Hopkins University wanted to ask a broader question: can psilocybin, given together with psychological support, reduce symptoms in adults with major depressive disorder (MDD, the medical term for clinical depression)?
To test this, they compared people who started the program right away with people who had to wait eight weeks before starting.
Who took part and what happened
The study enrolled 27 adults aged 21 to 75 with major depressive disorder between 2017 and 2019. None of them were taking antidepressants during the study. They were randomly split into two groups (randomized, meaning chance decided who went where):
- Immediate group (15 people) started treatment right away.
- Delayed group (12 people) waited eight weeks first. This is called a waiting-list control. It lets researchers see what happens to depression over time without the treatment.
Each person had two psilocybin sessions, about a week and a half apart. The first dose was 20 mg per 70 kg of body weight, the second 30 mg per 70 kg. Around these sessions, they received about 11 hours of preparation and support from trained staff. 24 of the 27 people completed everything.
Depression was measured with the GRID-HAMD, a clinician-rated scale where higher scores mean more severe depression. At the start, the average score was about 23, which counts as severe.
What they found
The difference between the two groups was large.
- In the immediate group, the average score dropped to 8.0 one week after the second session and was 8.5 four weeks after.
- In the delayed group, scores at the same points in time stayed high: 23.8 and 23.5.
Across everyone who completed the program, the study found:
- 71% had a clinically meaningful response (at least a 50% drop in score) at both one week and four weeks.
- 54% were in remission at four weeks (a score of 7 or lower, meaning few or no symptoms on this scale).
Participants' own ratings told a similar story. On a self-report questionnaire, average scores fell from 16.7 before treatment to 6.3 just one day after the first session, and stayed around 6 at four weeks.
These are large changes for a study of this kind. They should still be read with care, for the reasons below.
What this study does not tell us
- It was very small. Only 24 people completed it. Small studies can show bigger effects than larger ones later confirm.
- There was no placebo. Everyone knew whether they were getting psilocybin or waiting. Hope, expectations, and the attention of supportive staff may explain part of the improvement.
- It was short. The main results cover only four weeks after the second session. (A later follow-up by the same team, described separately, looked at 12 months.)
- The group was not diverse. Most participants were white and well educated. People at higher risk of suicide, people with certain other conditions, and people taking antidepressants were not included.
- A correction was published. The journal later corrected some effect sizes and one response rate. The authors stated the corrections did not change the direction or conclusions of the findings.
Why it matters
This was one of the first randomized trials to look at psilocybin for ordinary major depression, rather than depression linked to a serious illness or depression that had resisted other treatments. The results were strong enough to justify larger, more rigorous trials, and several have followed.
It also shows how much the setting matters. Participants were carefully screened, prepared over many hours, and supported by trained staff before, during, and after each session. The study tested psilocybin as part of that whole package, not on its own.
This is a summary of published research for general information. It is not medical advice. The study took place in a clinical research setting with medical screening and professional support.
Source: Davis AK, Barrett FS, May DG, Cosimano MP, Sepeda ND, Johnson MW, Finan PH, Griffiths RR (2021). Effects of Psilocybin-Assisted Therapy on Major Depressive Disorder: A Randomized Clinical Trial. JAMA Psychiatry, 78(5), 481–489. doi:10.1001/jamapsychiatry.2020.3285 · PubMed · Full text
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