A 2026 psilocybin study renews the oldest question

What the study did

• 28 healthy, entirely psychedelic-naive adults, placebo-controlled within-subjects design: a 1 mg dose first, then 25 mg.
• Single 25 mg psilocybin dose vs. 1 mg control.
• Follow-up one month later.

What it found

After the 25 mg dose — and not after the 1 mg control — participants showed greater well-being, insight, and cognitive flexibility at one month. Increases in brain entropy in the first hours predicted greater insight the next day, and insight predicted greater well-being at one month. The team also reported white-matter changes a month later, and notes that a sample of 28 needs replicating in larger studies.

Why it matters here

The study reframes a question Seaich was asking in 1959: what is the experience, and what does it do? A philosopher’s first-person evaluation from the first research era reads well beside the current science: it asks what the experience shows, which is the question these trials are now measuring.

Source: Lyons et al., “Human brain changes after first psilocybin use,” Nature Communications 17, 3977 (2026), DOI 10.1038/s41467-026-71962-3, published May 5, 2026. This brief is not medical advice.

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