Placebo

A placebo is any medication or treatment expected to have no physiological effect; the generally synonymous term sham treatment is sometimes used to describe a surgical or other procedure, more visible than a pill. According to the United States National Library of Medicine, a placebo is defined as a "dummy medication or treatment. Although placebos originally were medicinal preparations having no specific pharmacological activity against a targeted condition, the concept has been extended to include treatments or procedures, especially those administered to control groups in clinical trials in order to provide baseline measurements for the experimental protocol."

Placebo versus placebo effect

Placebo is different from a placebo effect, which is defined as an "effect usually, but not necessarily, beneficial that is attributable to an expectation that the regimen will have an effect, i.e., the effect is due to the power of suggestion" Thus the placebo effect can be a component of the effect of a treatment that has a true physiologic role; whereas a placebo has no intention of physiologic benefit.

The placebo effect is very common. In a randomized controlled trial of pregabalin for fibromyalgia the following occurred:

A randomized controlled trial of
pregabalin versus placebo
for fibromyalgia

study group	Patients reporting at least "much" improvement in their pain
pregabalin	43%
placebo	35%

Among the patients who received pregabalin, most of the benefit was due to placebo effect. The benefit due to the drug was 43% minus 35% or 8%. Thus if 100 patients receive pregabalin:

• 35 will improve due to placebo effect
• 8 will improve due to pregabalin (number need to treat is 100/8 or 13)
• 57 will not improve

Many doctors report prescribing medications in part for the placebo effect.

Purpose

Placebos originally were medicinal preparations having no specific pharmacological activity against a targeted condition. They have been used as a means of suggestion to individual patients. A randomized controlled trial found that placebo medications that the patient perceives as more expensive will have more placebo effect than placebos that are percieved as less expensive.

In any medical study, every patient- including those of a control group, if any- should be assured of the best proven diagnostic and therapeutic method. From The Declaration of Helsinki

The more common use of placebos is as for the patients in the control group of a randomized controlled trial. The World Medical Organization's interpretation of the Declaration of Helsinki, says placebo controls are unethical if there is a standard treatment for the disease being studied. When no treatment is available, placebo controls are ethical. This is by no means agreed by all medical scientists.