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Cebocap placebo capsules. Like placebos, nocebos have no medicinal effect. However, they are perceived by patients to be harmful due to a previous negative perception.

Borrowed from Latin nocēbō (I will harm), the first-person singular future active indicative form of noceō (I harm), by analogy with placebo. The word was coined by Walter P. Kennedy in a 1961 article entitled “The Nocebo Reaction” (see quotation).



nocebo (plural nocebos)

  1. (pharmacology, also attributive) A substance which a patient experiences as harmful due to a previous negative perception, but which is in fact pharmacologically (medicinally) inactive. [from 1961]
    • 1961 September, Walter P. Kennedy, “The Nocebo Reaction”, in Medical World, volume 95, London: Medical Practitioners' Union, ISSN 0025-7621, OCLC 714999966, PMID 13752532, page 203:
      It is somewhat surprising that little attention has been drawn to the existence of the contrary effect [to the placebo] – which I may call the nocebo reaction.
    • 2009 April 25, Stuart Blackman, “Why health warnings can be bad”, in Financial Times:
      In the case of the nocebo, it is negative expectations that become self-fulfilling prophecies.
    • 2014 May 15, Jennifer Welsh, “Researchers who Provided Key Evidence for Gluten Sensitivity have now Thoroughly Shown that It Doesn’t Exist”, in Business Insider[1], archived from the original on 2 July 2017:
      It seems to be a "nocebo" effect – the self-diagnosed gluten sensitive patients expected to feel worse on the study diets, so they did.


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  1. first-person singular future active indicative of noceō