A small study of 15 healthy adults found no statistically significant overall increase in a brain marker associated with synapses one week after a single dose of psilocybin. But participants who took the drug in a calm room with music reported more intense mystical-type experiences than those who took it inside an MRI scanner, and their scans showed a larger change in the marker.
The research, published in Translational Psychiatry, measured SV2A, a protein found at synapses, using positron emission tomography (PET). Synapses allow nerve cells to communicate, and researchers study changes in them as one possible way to understand the brain’s capacity to adapt. SV2A is an indirect measure of synaptic density, rather than a direct count of connections.
The first five participants took psilocybin while lying in an MRI scanner and completing imaging tasks. The remaining ten took it in a dedicated room while listening to a selected music playlist. Two facilitators offered psychological support in both settings. PET scans were taken before dosing and again a week later, with measurements focused on the frontal cortex and hippocampus.
Across all participants, average changes in SV2A were small, at around 2% to 3%, and were not statistically significant. The study ended early after an interim analysis indicated it was unlikely to reach its planned target. The researchers therefore did not establish that psilocybin increased the measured synaptic marker overall.
In exploratory comparisons, the room group reported more intense mystical-type experiences and more positive lasting effects at three months. The groups did not differ in reported negative lasting effects. SV2A rose by an average of about 5% to 6% in the frontal cortex and hippocampus among participants in the room, while the scanner group showed no increase. The difference between settings was statistically significant in the frontal cortex, but not in the hippocampus; the increase within the room group was not statistically significant by itself.
More intense mystical-type experiences were also associated with larger increases in SV2A, although that association was not statistically significant. The authors describe the differences between settings as preliminary and hypothesis-generating, rather than conclusive. They suggest a supportive environment could encourage positive experiences and a sense of safety, while the scanner’s noise and confinement might be distracting or stressful.
The study’s small sample limits what can be concluded. Participants were not randomly assigned: the five people in the scanner were the first enrolled. There was no placebo group, and the settings differed in several ways, including music, confinement and imaging tasks. The study involved healthy adults, not people receiving psilocybin as treatment, and its findings may not apply to clinical use.
Sources: PsyPost.