The word placebo is derived from the Latin verb "to please" and, as early as 1811, appeared in the Hooper's Medical Dictionary as a medical treatment aimed at pleasing - a placebo was defined as "an epithet given to any medication adopted more to please than to benefit the patient (Hooper 1817)." In the modern day era, Tilburt et al. refer to the placebo effect as "positive clinical outcomes caused by a treatment that is not attributable to its known physical properties or mechanism of action (Tilburt et al. 2008)."
Despite the lack of specific action of the placebo on the condition being treated, the placebo often provides benefit. In 1955, Henry Beecher, the first chairman of anesthesia at Massachusetts General Hospital, published a seminal article, "The Powerful Placebo," in which he observed a high rate of response to placebo administration. In this article, he observed, "It is evident that placebos have a high degree of therapeutic effectiveness in treating subjective responses, decided improvement, interpreted under the unknown technique as a real therapeutic effect, being produced in 35.2 ± 2.2% of cases (Beecher 1955)." Beecher observed this high degree of therapeutic effectiveness across a variety of clinical conditions, the breadth of which has been confirmed in subsequent scientific trials (Table 11.1). Since its publication, Beecher's article has become one of the most cited analyses of the powerful therapeutic effect of the placebo.
In recent years, however, the magnitude of the placebo effect has been questioned. Even the results of Beecher's landmark article have been criticized because none of the studies he referenced was properly controlled. In fact, recent reviewers have concluded that in fact no evidence of placebo effect could be found in any of the original studies cited by him (Kiene 1997). Nevertheless, the use of the placebo continues to be ubiquitous in clinical medicine today, both as a clinical intervention and as a research tool.
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