Sometimes, placebos work—but how?
Simply participating in a medical-research trial sometimes improves a person's health. That's why investigators use placebos—inert pills or other dummy treatments—and make both study participants and staff unaware of whether a person is receiving an active treatment or not. Anywhere from 10 to 100 percent of the people taking placebos in trials see their symptoms wane. In such a test, a drug is considered to be beneficial only if it can beat the placebo.
Many studies suggest that problems like pain and depression respond particularly well to placebos. Blood pressure, cholesterol concentration in the blood, and heart rate are also affected by placebos, as are warts. On average, about a third of people taking placebos in studies report a benefit.