Psilocybin-induced changes in electroencephalography link acute and long-term effects.
Marek Nikolič, Tom Froese, Pedro A M Mediano et al.
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In 30 seconds
This double-blind, placebo-controlled crossover trial examined electroencephalographic changes after psilocybin in 20 healthy participants. Psilocybin acutely reduced alpha/beta power and increased gamma-band signal diversity at 1–3 hours, with these measures returning to baseline at 6 hours. Greater gamma diversity was associated with stronger acute psychological effects (r = 0.71). At 24 hours, lower delta/theta power correlated with positive life changes reported at 4 weeks (r = -0.47 to -0.57), independently of acute psychological intensity. The findings distinguish acute EEG effects from sub-acute changes associated with later self-reported outcomes.
Key findings
- Alpha/beta power decreased and gamma-band signal diversity increased at 1–3 hours, returning to baseline at 6 hours.
- Gamma diversity correlated with acute psychological effects (Brief Psychiatric Rating Scale, r = 0.71); increases were largest in participants with lower baseline complexity.
- At 24 hours, reduced delta/theta power correlated with Positive Life Changes at 4 weeks (r = -0.47 to -0.57), independently of acute psychological intensity.
Why it matters
The results suggest that EEG changes associated with later self-reported positive life changes may occur after acute drug effects have subsided. This distinction may help research characterize the time course of psilocybin’s effects and investigate whether sub-acute neurophysiological measures relate to longer-term outcomes. The findings are preliminary and do not establish that these EEG changes cause therapeutic benefit.
What to keep in mind
The trial included 20 healthy participants, and the reported longer-term association was with self-reported Positive Life Changes rather than an established clinical outcome.