Psilocybin-induced changes in electroencephalography link acute and long-term effects
Marek Nikolič, Tom Froese, Pedro A. M. Mediano, Vlastimil Koudelka, Jiřı́ Horáček, Filip Tylš, Tomáš Páleníček
Journal of Psychopharmacology September 4, 2026 DOI: 10.1177/02698811261473445 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Randomized controlled trial (crossover) Placebo-controlled Double-blind Peer reviewed |
|---|---|
| Sample size | 20 |
| Population | Healthy participants (10 females) |
| Intervention | Psilocybin |
| Dose | ~0.26 mg/kg |
| Duration | 24-hour sub-acute phase with 28-day follow-up |
| Measures | Brief Psychiatric Rating Scale, Persisting Effects Questionnaire |
| Topics | Psilocybin |
| Key findings | Psilocybin acutely reduced alpha/beta power and increased gamma-band signal diversity, returning to baseline by 6 hours. Increased gamma diversity correlated with acute psychological effects (r = 0.71). At 24 hours, reduced delta/theta power correlated with positive life changes at 4 weeks (r = −0.47 to −0.57), independent of acute psychological intensity. |
Abstract
Background: Psilocybin’s therapeutic potential is neurophysiologically characterized by acute alpha power reductions and increased entropy. However, the systematic time-course of these changes from administration through the 24-hour sub-acute phase remains poorly characterized.
Methods: In a double-blind, placebo-controlled, crossover trial ( N = 20, 10 females), healthy participants received a medium dose ∼0.26 mg/kg of psilocybin. High-density resting-state electroencephalography and psychological states were assessed at baseline, 1, 3, 6, and 24 hours, with a 28-day follow-up.
Results: Psilocybin acutely decreased alpha/beta power and increased gamma-band signal diversity (1–3 hours; returning to baseline at 6 hours). Increased gamma diversity correlated with acute psychological effects (Brief Psychiatric Rating Scale, r = 0.71), with the largest increases observed in participants with lower baseline complexity. At 24 hours, reduced delta/theta power correlated with Positive Life Changes (Persisting Effects Questionnaire) at 4 weeks ( r = −0.47 to −0.57) but was independent of acute psychological intensity.
Conclusion: Our findings corroborate known acute effects while identifying a distinct sub-acute “afterglow” associated with long-term outcomes. The dissociation between acute psychology and 24-hour spectral shifts suggests that therapeutic benefits may be driven by sub-acute reductions in top-down cortical hierarchy. These results highlight the significance of the sub-acute window for psychological transformation and suggest normalized diversity as a viable baseline biomarker of individual responsiveness to psychedelic intervention.