The Placebo Effect

The placebo effect is the measurable improvement a patient can show after receiving a treatment with no active ingredient, such as a sugar pill, produced by expectation and the experience of being treated rather than by any pharmacological action. It is recorded here as a methodological concept rather than a medical finding: it is the baseline that the controlled trial and double-blind design exist to separate a real treatment's effect from, so that a new drug is judged against how much a patient would have improved anyway from believing they were being treated. The physician Henry Beecher's 1955 paper The Powerful Placebo is credited with naming the effect and giving it its modern place in trial design, though the underlying observation that belief and expectation affect reported symptoms is older than Beecher's paper.