"The physician's belief in the treatment and the patient's faith in the physician exert a mutually reinforcing effect; the result is a powerful remedy that is almost guaranteed to produce an improvement and sometimes a cure." -- Petr Skrabanek and James McCormick, Follies and Fallacies in Medicine, p. 13.
The placebo effect is the measurable, observable, or felt improvement in health not attributable to treatment. This effect is believed by many people to be due to the placebo itself in some mysterious way. A placebo (Latin for "I shall please") is a medication or treatment believed by the administrator of the treatment to be inert or innocuous. Placebos may be sugar pills or starch pills. Even "fake" surgery and "fake" psychotherapy are considered placebos. Researchers and medical doctors sometimes give placebos to patients. Anecdotal evidence for the placebo effect is garnered in this way. Those who believe there is scientific evidence for the placebo effect point to clinical studies, many of which use a control group treated with a placebo. Why an inert substance, or a fake surgery or therapy, would be effective is not known.
“The psychological theory: it's all in your mind”
Some believe the placebo effect is psychological, due to a belief in the treatment or to a subjective feeling of improvement. Irving Kirsch, a psychologist at the University of Connecticut, believes that the effectiveness of Prozac and similar drugs may be attributed almost entirely to the placebo effect. He and Guy Sapirstein analyzed 19 clinical trials of antidepressants and concluded that the expectation of improvement, not adjustments in brain chemistry, accounted for 75 percent of the drugs' effectiveness (Kirsch 1998). "The critical factor," says Kirsch, "is our beliefs about what's going to happen to us. You don't have to rely on drugs to see profound transformation." In an earlier study, Sapirstein analyzed 39 studies, done between 1974 and 1995, of depressed patients treated with drugs, psychotherapy, or a combination of both. He found that 50 percent of the drug effect is due to the placebo response. A person's beliefs and hopes about a treatment, combined with their suggestibility, may have a significant biochemical effect. Sensory experience and thoughts can affect neurochemistry. The body's neurochemical system affects and is affected by other biochemical systems, including the hormonal and immune systems. Thus, it is consistent with current knowledge that a person's hopeful attitude and beliefs may be very important to their physical well-being and recovery from injury or illness. However, it may be that much of the placebo effect is not a matter of mind over molecules, but of mind over behavior. A part of the behavior of a "sick" person is learned....