nocebo
noun
Did you know?
Nocent has been in the English language as a word for "harmful" since the 15th century. It comes from Latin nocēre, meaning "to harm." Latin nocebo is a close relative that means "I will be harmful" and that contrasts with placebo, meaning "I shall please." People in medicine began using "placebo" for inert preparations prescribed solely for a patient's mental relief, and not for relieving a disorder, in the late 18th century. As doctors began to observe the effects of placebos, some noticed that the harmless preparations actually sometimes caused detrimental effects on the patient's health. English speakers began using the word nocebo for substances causing such adverse reactions in patients in 1961.
Examples of nocebo in a Sentence
TIME, 4 Apr. 2024
As such, the researchers argue that highlighting the potential for nocebo responses could reduce side effects and help improve vaccine uptake.
—Beth Mole, Ars Technica, 19 Jan. 2022
Hudson says there may be a placebo effect available to marathoners who believe strongly in the benefits of a training volume reduction, but the current narrative seems more likely to produce the opposite effect on performance, a nocebo.
—Leo Spall, Outside Online, 11 Oct. 2019
Expectations are key to both placebo and nocebo.
—Elizabeth Preston, Discover Magazine, 9 July 2014
Cite this Entry
“Nocebo.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/nocebo. Accessed 4 Nov. 2025.
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nocebo
noun
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