The Nocebo Effect: How Expectations Can Cause Harm

What is this page about?

An explainer of the nocebo effect, the mind's capacity to produce real physical harm from negative expectation (the harmful counterpart of placebo), opening with a trial participant whose vital signs collapsed after overdosing on placebo pills he believed were antidepressants. It covers the biology of negative expectation, how warning labels induce side effects (finasteride, beta-blockers, aspirin, COVID vaccines), the inactive-control problem in trials, the role of doctor-patient communication and the consent dilemma, mass psychogenic illness, and how to minimize nocebo effects without sacrificing honesty.

What has been corrected on this page?

Every accepted correction to this page is recorded with the exact change, so readers can see how the page improved over time.

1. 11 July 2026 · corrected by Emir Baycan

   4 corrections applied: SAMSON trial was Howard et al. (2020); Gupta et al. 2017 is the separate ASCOT-LLA analysis | Mondaini et al. finasteride nocebo study was published in 2007, not 2009 | Mondaini et al. was published in 2007, not 2009 | Haas et al. (2022) COVID-19 vaccine nocebo meta-analysis was published in JAMA Network Open, not JAMA Internal Medicine

   Before

   A 2009 study of finasteride for benign prostatic hyperplasia found that patients who were warned about sexual dysfunction experienced it at nearly twice the rate of patients who were not informed. (also: Gupta et al. 2017 SAMSON; Haas et al. JAMA Internal Medicine - all pre-fixed in body)

   After

   A 2007 study of finasteride for benign prostatic hyperplasia found that patients who were warned about sexual dysfunction experienced it at nearly twice the rate of patients who were not informed.

   Why: Article body already correctly cites Howard et al. 2020 SAMSON trial, Mondaini et al. 2007, and Haas et al. 2022 in JAMA Network Open. However the FAQ JSON-LD block still had a stale '2009' date for the Mondaini finasteride nocebo study (should be 2007, matching the body/bibliography). Fixed the FAQ answer and re-encoded via the standard base64/json op-sequence; verified clean on re-fetch.

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