placebo effect

American

[pluh-see-boh] / pləˈsi boʊ /

noun

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

placebo effect British

noun

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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of placebo effect

First recorded in 1945–50

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The company is leaning toward a trial that compares patients receiving the therapy against a control group receiving standard treatments and a “sham” procedure to rule out any placebo effect.

From Barron's • Jun. 17, 2026

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

From Science Daily • May 22, 2026

People swear by it, but a lot of these things have a placebo effect.

From The Wall Street Journal • Jan. 5, 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

It must have been a placebo effect, but it was a great placebo effect.

From "It’s Kind of a Funny Story" by Ned Vizzini

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023