'By definition, a placebo is an inert, innocuous substance that has no effect on your body. Placebos, such as sugar pills, are therefore used as controls against which the effects of modern-day medical treatments are measured.
However, the placebo-effect, in which a patient believes he or she is getting an actual drug and subsequently feels better, despite receiving no “active” treatment at all, has become a well-recognized phenomenon.
A number of studies have revealed that placebos can work just as well as potent drugs. Sham surgery has even been shown to produce results that are equal to actual surgery!
Indeed, mounting research suggests this "power of the mind," or power of belief, can be a very healing force. Studies into the placebo effect also show that many conventional treatments "work" because of the placebo effect and little else.'