Carhart-Harris · Neuropharmacology 2018 · Narrative review · n=?

The entropic brain - revisited.

Cited 559 times in the scientific literature.

Level 5 - mechanism / opinion, no new human data

Narrative review and theoretical framework without systematic review methodology or new empirical human data.

PubMed 29548884 · doi:10.1016/j.neuropharm.2018.03.010 · record verified 2026-08-28

What was done

This is a narrative review revisiting the entropic brain hypothesis four years after its original publication. The author synthesizes findings from separate and independent studies regarding the entropy of spontaneous brain activity, measures of brain criticality, and conscious states under the influence of psychedelics.

What was found

The abstract reports no quantitative data, numerical values, or effect sizes. It qualitatively describes that increased entropy of brain activity in the psychedelic state is supported by independent studies, highlights evidence for greater brain criticality under psychedelics, and links this state to increased sensitivity to set and setting.

Why it matters

This paper refines a widely cited theoretical framework connecting brain entropy to the informational richness of consciousness, suggesting specific entropy measures to explore psychiatric disorders like depression and disorders of consciousness.

Limits

As a narrative review, it lacks a systematic literature search, formal risk-of-bias assessment, or pooled quantitative data. No specific sample sizes, demographic parameters, or empirical numbers are reported in the abstract.

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