For alternative meanings, see Placebo (disambiguation)

A placebo is a medical treatment (operation, therapy, chemical solution, pill, etc.), which is administered as if it were a therapy, but which has no therapeutic value other than the placebo effect.

Placebo comes from the Latin for "I will please".

Experimenters typically use placebos in the context of a clinical trial, in which a "test" group of patients receive the therapy being tested, and a "control" group receives the placebo. It can then be determined if results from the "test" group exceed those due to the placebo effect. If they do, the therapy or pill given to the "test" group is assumed to have had an effect.

Often during these clinical trials, placebos have a positive or negative clinical effect on subjects tested. Most of these effects are presumed to be psychological in nature but placebo effects can at times be predictable and measurable.

A treatment like a placebo but which has a harmful result is called a nocebo (Latin for "I will harm").

See also

• Placebo effect
• Scientific method

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