Psilocybin in long-term meditators: Effects on default mode network functional connectivity and retrospective ratings of qualitative experience
Barrett, F. S., Griffiths, R. R., Johnson, M. W.
This double-blind, placebo-controlled study (n=16) examined the effects of high-dose psilocybin on subjective experience and brain connectivity in long-term meditators. Results indicate that psilocybin induced profound personal meaning and altered functional connectivity within the default mode network (DMN) and between the DMN and hippocampus, effects that were observable the day after dosing.
Abstract
Aims: Descriptions of meditation experiences can bear striking similarity to descriptions of some experiences with classic (serotonergic) hallucinogens. Neuroimaging studies reveal striking overlap in the effects of psilocybin and the effects of meditation on functional connectivity of the default mode network (DMN). This ongoing study explored the effects of psilocybin on subjective experience and DMN connectivity in long-term meditators.Methods: 16 meditators (mean lifetime meditation = 4206 h) received either a placebo (n = 8) or a high dose psilocybin (n = 8) capsule before a laboratory session. Retrospective self-report measures of subjective experience and resting-state fMRI data were collected the day after the session. Seed-based functional connectivity analyses were applied to fMRI data. Self-report measures and functional connectivity of the DMN were compared between placebo and psilocybin groups.Results: Participants who received psilocybin attributed significantly greater meaning, spiritual significance, psychological challenge, and psychological insight to their session experiences than those who received placebo. 75% of participants in the psilocybin group rated the experience to be in the top 10 most meaningful experiences of their life. Participants who received psilocybin also showed lower functional connectivity between hippocampal and posterior DMN regions and greater functional connectivity among DMN regions than those who received placebo.Conclusions: Participants attributed substantial meaning to their high-dose psilocybin experience, and showed changes in brain function the day after a high dose of psilocybin. Further research should explore the relationship of these enduring changes in brain function to abuse liability and therapeutic outcomes with psilocybin.