Human brain changes after first psilocybin use

Summary & key facts

Researchers gave 28 healthy people who had never used psychedelics a single high dose of psilocybin and scanned their brains before and after. They saw short-term increases in brain signal complexity and signs of small changes in brain wiring that lasted up to a month. Those early brain changes were linked to better psychological insight and higher well-being one month later. All effects happened after the high dose and did not happen with a tiny placebo dose. The study is small and exploratory, so it shows interesting links but does not prove psilocybin is a treatment for any condition.

Key facts:

• 28 healthy people who had never used psychedelics took part in the study and each person was measured before and after taking a single high dose of 25 mg psilocybin.
• Brain electrical recordings showed higher cortical signal entropy, a measure of more complex brain activity, at one and two hours after the high dose. That early increase predicted who reported better psychological well-being one month later.
• Brain scans that look at water movement in brain wiring found decreased axial diffusivity in prefrontal-to-deep-brain tracts one month after the high dose. That change was linked to a numerical drop in how separated brain networks were from each other, a feature called modularity.
• People reported increases in cognitive flexibility, psychological insight, and overall well-being one month after the high dose of psilocybin.
• All of these effects were only seen after the 25 mg dose. No similar brain or psychological changes were found after a 1 mg placebo dose.
• The study is exploratory and used a small group of healthy volunteers. That means the findings are interesting but preliminary and do not by themselves prove psilocybin is safe or effective as a treatment.

Abstract

Psychedelics have robust effects on acute brain function and long-term behavior but whether they also cause enduring functional and anatomical brain changes is largely unknown. In an exploratory, placebo-controlled, within-subjects, electroencephalography (EEG), and magnetic resonance imaging (MRI) study in 28 healthy, entirely psychedelic-naive participants, anatomical and functional brain changes are detected from one-hour to one-month after a single high-dose (25 mg) of psilocybin. Increases in cognitive flexibility, psychological insight, and well-being are seen at one-month. Diffusion tensor imaging (DTI) done before and one-month after 25 mg psilocybin reveals decreased axial diffusivity bilaterally in prefrontal-subcortical tracts that correlate with decreases in brain network modularity (fMRI) over the same month. Enduring functional brain changes are largely absent, but network modularity change (numerical decrease) negatively correlates with well-being change (significant increase), in line with previous findings in depression. Increased cortical signal entropy (EEG) at 1- and 2-hours post-dosing predicts improved psychological well-being at one-month. Next-day psychological insight mediates the entropy to well-being relationship. All effects are exclusive to 25 mg psilocybin; no effects occur with a 1 mg psilocybin placebo.

Topics

Cannabis and Cannabinoid Research Mental Health and Psychiatry Psychedelics and Drug Studies

Categories

Clinical Psychology Psychology Social Sciences

Tags

Hallucinogen Human brain Neuroscience Psilocybin Psychiatry Psychology

Substances

Psilocybin

Conditions & symptoms

Depression Sadness or low mood