Psilocybin's effect on human brain synaptic plasticity.
Annette Johansen, Pontus Plavén-sigray, Martin K Madsen, Anna Søndergaard, Catharina Messel, Maria Geisler, Arafat Nasser, Drummond E-W Mcculloch, Vincent Beliveau, Alexandra Vassilieva, Anton Lund, Szabolcs Lehel, Brice Ozenne, Dea S Stenbæk, Patrick M Fisher, Claus Svarer, Gitte M Knudsen
Translational psychiatry July 15, 2026 DOI: 10.1038/s41398-026-04285-y via PubMed
Summary
A single dose of psilocybin (0.3 mg/kg) did not produce a statistically significant increase in synaptic density across all fifteen healthy participants. However, those who received psilocybin in a therapeutic-like room reported more intense mystical-type experiences, longer-lasting psychological benefits, and showed greater increases in synaptic density in the frontal cortex and hippocampus compared to those dosed inside an MRI scanner. The findings indicate that environmental context modulates psilocybin's neuroplastic effects, with implications for psychedelic-assisted therapies.
Study at a glance
| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 15 |
| Population | Healthy individuals |
| Registration | NCT03289949 |
| Key finding | Psilocybin's effect on synaptic density is modulated by environmental context, with a therapeutic-like setting associated with greater increases in synaptic density and more intense mystical-type experiences than an MRI scanner setting. |
Abstract
Psychedelics such as psilocybin have been linked to enhanced neuroplasticity and symptom relief in affective disorders, but the neurobiological mechanisms and impact of environmental context remain unclear. Here, we tested whether a single dose of psilocybin (0.3 mg/kg) alters synaptic density in healthy individuals and whether setting-dependent subjective experience shapes this effect. Fifteen healthy participants had a psilocybin-induced psychedelic experience either inside an MRI scanner or in a therapeutic-like room. We assessed synaptic density changes by measuring the Synaptic Vesicle glycoprotein 2A in the frontal cortex and hippocampus with [¹¹C]UCB-J PET at baseline and one-week post-dose, and assessed subjective experiences immediately afterwards and at three months. Overall, we found no statistically significant increase in SV2A density. However, participants treated in the therapeutic-like setting exhibited more intense mystical-type experiences, longer-lasting psychological benefits, and greater increases in synaptic density than those dosed in the MRI scanner. These findings indicate that psilocybin's neuroplastic effects are modulated by environmental context, with important implications for psychedelic-assisted therapies. ClinicalTrial: NCT03289949.