A year after psilocybin: did the changes in depression last?
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The question
In 2020, a small Johns Hopkins trial found that two psilocybin sessions with psychological support led to large drops in depression symptoms within four weeks. But depression often comes back. The obvious next question was: how long do these changes last?
This study followed the same participants for a full year after their second session to find out, and to check for any safety problems along the way.
Who took part and what happened
The original trial included 27 adults with major depressive disorder (MDD, the medical term for clinical depression). 24 of them completed both psilocybin sessions and all follow-up visits. Their average age was about 40, and two thirds were women.
Each person had two sessions, with doses of 20 mg and then 30 mg per 70 kg of body weight, plus about 11 hours of preparation and support. After that, researchers checked in at one week, four weeks, three months, six months, and twelve months.
Depression was measured with the GRID-HAMD, a clinician-rated scale where higher scores mean more severe symptoms. A score of 7 or lower counts as remission (few or no symptoms on this scale).
What they found
On average, the improvement held up over the year. Average scores were:
- 22.8 before treatment (severe range)
- 8.9 at four weeks
- 9.3 at three months
- 7.0 at six months
- 7.7 at twelve months
The share of people with a clinically meaningful response (at least a 50% drop in score) was 71% at four weeks and 75% at twelve months. The share in remission was 54% at four weeks and 58% at twelve months.
On safety, the study found no serious adverse events judged to be related to psilocybin during the follow-up year. One person reported a brief visual distortion lasting about a minute, around three months after the second session. It did not return. Suicidal thoughts stayed low, and there were no suicide attempts or self-harm.
What this study does not tell us
- Other treatments came into play. By twelve months, 8 of the 24 participants (33%) had started or resumed daily antidepressants, and around 40% had some form of psychotherapy. For those people, we cannot tell how much of their state was due to psilocybin.
- There was no comparison group for the long term. Everyone in the follow-up had received psilocybin. Without a group that did not, the study cannot separate the drug's effect from hope, expectations, the support received, or natural change over time.
- Participants knew what they got. There was no blinding (hiding which treatment someone received).
- It was small and not diverse. 24 people, mostly white and non-Hispanic. People judged to be at higher suicide risk were excluded.
- Averages hide individuals. Some people improved a lot, others less, and some needed additional help.
The authors themselves say larger studies are needed to fully understand safety.
Why it matters
Most depression treatments are judged over weeks or a few months. Here, two sessions were followed by improvement that, on average, was still present a year later in this small group. That is worth taking seriously, and worth testing properly in larger trials.
The details matter too. This was a carefully screened group, supported by trained staff, with regular check-ins for a year. And a third of participants still went on to use antidepressants. Lasting change, for many people, seems to come from more than a single experience.
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: Gukasyan N, Davis AK, Barrett FS, Cosimano MP, Sepeda ND, Johnson MW, Griffiths RR (2022). Efficacy and safety of psilocybin-assisted treatment for major depressive disorder: Prospective 12-month follow-up. Journal of Psychopharmacology, 36(2), 151–158. doi:10.1177/02698811211073759 · PubMed · Full text
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