The placebo effect only began to come under scientific scrutiny in the 1950s, when double-blind clinical trials were introduced for testing the efficacy of pharmacological agents. Part of the group receiving only the placebo would claim beneficial effects. They can, in many situations, but only if we distinguish between disease and illness. A disease is an abnormal state of the body, something a physician can see, measure or otherwise identify. A cancerous growth, a lung infection or a blocked artery are such examples.
Illness is what a patient feels and suffers, for example, pain, nausea, fatigue or insomnia.
It has been firmly established by many studies that placebos can lessen pain and other subjective suffering in some patients, at least for short periods. But it is also recognized that certain mind-body interactions do occur and may play a role in some instances. The mind influences certain physiological functions. The body has a remarkable ability, with its immune system, to fight off diseases and promote self-healing. It constantly depends on this system, whether the threats arise from the breakdown or misbehavior of its own cells or invasion by bacteria, viruses and parasites.