Placebo effect: Also called the placebo response. A remarkable phenomenon in which a placebo — a fake treatment, an inactive substance like sugar, distilled water, or saline solution — can sometimes improve a patient’s condition simply because the person has the expectation that it will be helpful. Expectation to plays a potent role in the placebo effect. The more a person believes they are going to benefit from a treatment, the more likely it is that they will experience a benefit.
To separate out this power of positive thinking and some other variables from a drug’s true medical benefits, companies seeking governmental approval of a new treatment often use placebo-controlled drug studies. If patients on the new drug fare significantly better than those taking placebo, the study helps support the conclusion that the medicine is effective. The power of positive thinking is not a new subject.Research is ongoing as to why some people experience changes even when they are only receiving a placebo.