Many illnesses are psychological and studies have shown that when a person is unhappy or under stress, he or she is more likely to fall sick or suffer from an ailment. Similarly, it is believed that a person can be cured of an illness simply by the power of suggestion. A placebo is a preparation which does not contain any pharmaceutically active ingredient, but still is effective as a medicine.
Also known as the effect of expectations, the patients symptoms are alleviated after the placebo is given to the patient, since the patient expects or believes that it will work. The placebo is usually a sugar coated pill without any active ingredient and is prescribed by an authority figure like a trusted doctor. This effect has been observed and studied for nearly a century now.
Placebos are more effective in treating psychological illnesses like depression, withdrawal symptoms and tiredness. Patients who have been conditioned to trust the doctor and are motivated to feel better have shown the most pronounced change in their condition. Placebos for treatment of pain are more effective when the pain is pre existing.