A placebo ( /pləˈsiboʊ/ plə-SEE-boh; Latin placēbō, “I shall please” from placeō, “I please”) is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient. Sometimes patients given a placebo treatment will have a perceived or actual improvement in a medical condition, a phenomenon commonly called the placebo effect.

In medical research, placebos are given as control treatments and depend on the use of measured deception. Common placebos include inert tablets, sham surgery, and other procedures based on false information. However, placebos can also have a surprisingly positive effect on a patient who knows that the given treatment is without any active drug, as compared with a control group who knowingly did not get a placebo.

In one common placebo procedure, however, a patient is given an inert pill, told that it may improve his/her condition, but not told that it is in fact inert. Such an intervention may cause the patient to believe the treatment will change his/her condition; and this belief may produce a subjective perception of a therapeutic effect, causing the patient to feel their condition has improved — or an actual improvement in their condition. This phenomenon is known as the placebo effect.

Placebos are widely used in medical research and medicine, and the placebo effect is a pervasive phenomenon; in fact, it is part of the response to any active medical intervention. Archie Cochrane suggested in 1972 "It is important to distinguish the very respectable, conscious use of placebos. The effect of placebos has been shown by randomized controlled trials to be very large. Their use in the correct place is to be encouraged "

The placebo effect points to the importance of perception and the brain's role in physical health. However, the use of placebos as treatment in clinical medicine (as opposed to laboratory research) is ethically problematic as it introduces deception and dishonesty into the doctor-patient relationship. The United Kingdom Parliamentary Committee on Science and Technology has stated that: "...prescribing placebos... usually relies on some degree of patient deception" and "prescribing pure placebos is bad medicine. Their effect is unreliable and unpredictable and cannot form the sole basis of any treatment on the NHS."

Since the publication of Henry K. Beecher's The Powerful Placebo in 1955, the phenomenon has been considered to have clinically important effects. This view was notably challenged when, in 2001, a systematic review of clinical trials concluded that there was no evidence of clinically important effects, except perhaps in the treatment of pain and continuous subjective outcomes. The article received a flurry of criticism, but the authors later published a Cochrane review with similar conclusions (updated as of 2010). Most studies have attributed the difference from baseline till the end of the trial to a placebo effect, but the reviewers examined studies which had both placebo and untreated groups in order to distinguish the placebo effect from the natural progression of the disease. However these conclusions have been criticized because of the great variety of diseases—more than 40—in this metastudy. The effect of placebo is very different in different diseases. By pooling quite different diseases the results can be leveled out.

Read more about Placebo:  Definitions, Effects, and Ethics, History, Mechanism of The Effect, Symptoms and Conditions

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