Medic Henry Beecher discovered the placebo effect during World War II while treating wounded American soldiers, according to BrainFacts.org. When Beecher ran out of morphine, he used a saline solution but continued telling the soldiers he was using morphine.
BrainFacts.org explains that of the soldiers receiving the saline, 40 percent reported that their pain improved. As of 2014, scientists still do not understand exactly how placebos work to relieve pain and other symptoms.
Scientists know that placebos stimulate the brain to release natural substances and that they change brain activity to simulate the effects of real medical treatments. Placebos take many forms, including injections, devices, pills and procedures. A doctor may even tell a patient that his condition is improving in order to produce a placebo effect.