Psilocybin’s effect on human brain synaptic plasticity

This secondary analysis of a psilocybin neuroimaging trial used [11C]UCB-J PET to measure synaptic density (SV2A) in 15 healthy participants one week after a single dose. A preplanned interim analysis found no significant increase in frontal or hippocampal binding, and the study was stopped for futility. In exploratory analyses, participants dosed in a calm intervention room rather than inside the MRI scanner reported stronger mystical-type experiences and greater positive persisting effects at three months, and showed larger synaptic increases, indicating that session environment shapes the response.