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

As early as 1999, Irving Kirsch, a lecturer at Harvard, began to explore the role of the placebo effect in antidepressant studies, asserting that the placebo response to medication was greater than any pharmacological effect.

From Salon • May 23, 2025

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