Nocebo effect
Genuine symptoms produced by the expectation of harm rather than by the exposure itself — the inverse of the placebo effect.
health
Last verified 12 August 2026.
- Category
- health
Definition
A nocebo response is a real, sometimes measurable symptom caused by a person's expectation that something will harm them. It is the mechanism the EHS provocation literature converges on: in 46 blinded experiments symptoms tracked what participants believed about the exposure rather than whether the field was actually present. Calling a symptom a nocebo response says nothing about whether it is real or disabling — it addresses only what triggered it, and therefore what is likely to help.
Sources
- rubin-2010 Idiopathic environmental intolerance attributed to electromagnetic fields (formerly 'electromagnetic hypersensitivity'): an updated systematic review of provocation studies — Rubin GJ, Nieto-Hernandez R, Wessely S — Bioelectromagnetics 31(1):1–11, 2010. peer-reviewed, link checked 2026-08-12.
- who-ehs Electromagnetic hypersensitivity (WHO backgrounder, December 2005; formerly Fact sheet 296) — World Health Organization, 2005. government, link checked 2026-08-12.
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