Tripping on context: Characteristics and predictors of placebo and nocebo psychedelic effects

Overview

1. Department of Psychology, Institute of Psychology, Psychiatry, and Neuroscience, King’s College London, London, UK
2. Department of Psychosis Studies, Institute of Psychology, Psychiatry, and Neuroscience, King’s College London, London, UK
3. Institute of Pharmaceutical Science, King’s College London, London, UK
4. Cultural and Social Neuroscience Research Group, Forensic and Neurodevelopmental Sciences, Institute of Psychology, Psychiatry, and Neuroscience, King’s College London, London, UK

Abstract

Psychedelic drugs are emerging as potentially efficacious tools for treating psychiatric conditions and probing the neural basis of consciousness. Although drug administration context is widely believed to shape psychedelic effects, it remains unclear whether it can independently generate placebo and nocebo effects resembling psychedelic experiences and side effects. In a pre-registered experiment, 78 non-clinical participants inhaled inert medical air under placebo and control conditions while completing a time perception task and a resting-state period. In the placebo condition, the gas was presented as nitrous oxide, whereas in the control, it was correctly identified. Placebo administration increased altered states of consciousness, ego dissolution, dissociation, and side effects, but did not significantly impact time perception. Predictive modelling indicated that placebo-induced psychedelic effects were predicted by trait responsiveness to verbal suggestion and absorption. These findings demonstrate that context alone can induce psychedelic effects, with implications for its causal role in psychedelic action.

Reproduced under the paper's license (CC BY), from the paper cited above.

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Data

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• osf:4ab7r — at OSF; found in the text, “Methods”

Data Availability Statement

Links to the pre-registration and data are presented in the manuscript.

Reproduced under the paper's license (CC BY), from the paper cited above.

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Version 2, 28 September 2026

• Authors: added Quinton Deeley (0000-0001-5306-0769); removed Quinton Deeley

Version 1, 27 September 2026: the first record

Recorded: type, journal, dates, 5 authors, 5 keywords, 1 funder, 98 references.

Cite

This paper

Stein, M. V., Butler, M., Chapman, S., Deeley, Q., & Terhune, D. B. (2026). Tripping on context: Characteristics and predictors of placebo and nocebo psychedelic effects. medRxiv (preprint). https://doi.org/10.64898/2026.05.31.26354539

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