" Dr Stewart Wolf took the placebo effect to the limit. He took two women who were suffering with nausea and vomiting, one of them pregnant, and told them he had a treatment which would improve their symptoms. In fact he passed a tube down into their stomachs (so that they wouldn’t taste the revolting bitterness) and administered ipecac, a drug that which should actually induce nausea and vomiting. Not only did the patients’ symptoms improve, but their gastric contractions—which ipecac should worsen—were reduced. His results suggest—albeit it in a very small sample—that a drug could be made to have the opposite effect to what you would predict from the pharmacology, simply by manipulating people’s expectations. In this case, the placebo effect outgunned even the pharmacological influences. More "

― Ben Goldacre , Bad Science