Tripping on context: Characteristics and predictors of placebo and nocebo psychedelic effects
medRxiv Preprint Server May 31, 2026 Madeline V. Stein, Matt Butler, Sarah Chapman et al. preprint
Context alone can produce psychedelic-like effects, even without an active drug. In a placebo experiment, 78 healthy participants inhaled inert medical air. When told it was nitrous oxide, they reported increased altered states of consciousness, ego dissolution, dissociation, and side effects, compared to when the gas was correctly identified as air. Time perception was not significantly affected. The strength of placebo-induced effects was predicted by individual traits of responsiveness to verbal suggestion and absorption. These results demonstrate that the context of drug administration plays a causal role in shaping psychedelic experiences.