placebo effect

American  

[pluh-see-boh] / pləˈsi boʊ /

noun

1. a reaction to a placebo manifested by a lessening of symptoms or the production of anticipated side effects.

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placebo effect British  

noun

1. med a positive therapeutic effect claimed by a patient after receiving a placebo believed by him to be an active drug See control group

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Etymology

Origin of placebo effect

First recorded in 1945–50

Example Sentences

The other half received a sham treatment designed to control for the placebo effect.

From Science Daily • May 22, 2026

They point to studies suggesting a strong caregiver placebo effect, with the only real change being the owner’s perception of their pet’s condition.

From The Wall Street Journal • May 17, 2026

“The placebo effect can also be very powerful, especially for treatments that require significant effort and cost.”

From Los Angeles Times • Sep. 12, 2025

He warned a pineal cyst should only be removed in extremely rare circumstances, and believes the operations' successful results could be explained by the "placebo effect".

From BBC • Dec. 4, 2024

As it happens, Denis Papin, who had qualified as a doctor, was the first to describe the placebo and the placebo effect, in a letter to Leibniz, 11 or 12 August 1704.

From "The Invention of Science" by David Wootton