What is the placebo effect?

The placebo effect is the tendency for an ineffective or completely non-functional treatment to have actual, measurable success when treating some medical condition, when measured against receiving no treatment at all. For example, a sugar pill may make someone suffering from pain feel better if they are told that's what it will do, despite the pill having no mechanism or active ingredient that would permit any physiological change. Similarly, random application of toothpicks by untrained personnel produces similar pain-relieving results to that of acupuncture therapy by "trained professionals", both of which produce results compared to no treatment at all.

The placebo effect is affected by variations in the placebo - fake injections may give different results than fake pills, placebos given by apparent doctors in lab coats may product different results than those administered by apparent lay people. Even the size, color, and shape of a fake pill may affect the outcome for the recipient.

In addition to beneficial effects, placebos may also induce artificial negative side-effects.

Why is it important in medicine?

It is important to account for the placebo effect in order to distinguish the actual effects of a given treatment being evaluated. If the placebo effect is not accounted for, then a treatment may appear to be effective, when really the treatment operates no better than a sugar pill or other placebo equivalent.

How is it controlled in pharmaceutical trials?

Typically it is controlled for by providing a placebo treatment to a control group, and evaluating the success of the treatment (and its side effects) against the placebo group, rather than against a group receiving no treatment at all.