Psilocybin made time feel slower and less precise in 24 healthy volunteers

The question

Does psilocybin change how people judge the passage of time, and do those changes match what they say they experience?

What they did

Twenty-four healthy volunteers took part in a double-blind, placebo-controlled study, meaning neither they nor the researchers knew when they received psilocybin or a placebo. Each person completed a “temporal bisection task”, a computer test where people judge whether a short interval is closer to a short or a long reference duration. Researchers measured two things: the bisection point (the interval judged as halfway) and the just noticeable difference (how finely someone can tell durations apart). They also used two questionnaires, the Hallucinogen Rating Scale and the Altered States of Consciousness scale, to capture what participants said they felt.

What they found

Under psilocybin, the bisection point shifted rightward compared with placebo (t(23) = 2.27, p = 0.033, g = -0.37), a pattern consistent with time feeling as though it were passing more slowly. Participants’ own reports on the two questionnaires also described time slowing down. The just noticeable difference increased under psilocybin (t(23) = 2.48, p = 0.021, g = -0.47), meaning people were less precise at telling durations apart. These effects were only significant for intervals longer than 2 seconds.

The fine print

The study included only 24 healthy volunteers, so the findings may not extend to people receiving psilocybin for a mental health condition. The effect sizes reported were small to moderate, and the outcome was a laboratory timing task, not a clinical or wellbeing measure. The abstract does not state the dose, the number of sessions, or whether blinding held despite psilocybin’s noticeable effects. This summary is based on the abstract alone.

What it means

In a controlled laboratory setting, psilocybin appeared to stretch and blur people’s sense of time for intervals over two seconds, and their objective task performance lined up with what they reported feeling. This is a basic science finding about perception, not evidence about treating any condition.

Evidence grade: Moderate. A double-blind, placebo-controlled study in healthy volunteers, but with only 24 people and a laboratory task rather than a health outcome.

This summary is based on the study’s published abstract.