A preprint is a version of a scientific paper that its authors post online, on servers such as medRxiv or PsyArXiv, before or while it goes through peer review. It makes new results available fast, and anyone can read it, but no journal has yet vetted it.
Preprints are increasingly part of psychedelic research. Two of the five psilocybin OCD studies with results were available only as preprints in October 2026 (Kelmendi et al., 2026; Tiwari et al., 2026). The Yale preprint reported that 9 of 13 people on psilocybin responded at one week, against none of 14 on niacin (Kelmendi et al., 2026). Trial protocols are posted as preprints too, such as a planned microdosing trial for depression, which has no results yet (Beidas et al., 2025).
A preprint’s numbers may change before publication, and some never get published. Journalists and readers should label them clearly, as this site’s journal does, and check later for a peer-reviewed version.
Sources
- Kelmendi et al., PsyArXiv preprint, 2026
- Tiwari et al., medRxiv preprint, 2026
- Beidas et al., OSF Preprints, 2025
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