Placebo--the forgotten drug.

The placebo effect is seen in patients who have been the target of intervention believed to lack specific action. This effect seems to be an important, and possibly the only, contribution to the positive effect of alternative medicine sometimes reported. The risks involved in the uncritical utilization of the placebo effect are, however, great and must be carefully considered. Most of the information available on this effect has been obtained from double-blind studies in connection with the introduction of new drugs. Depending on the kind of effect that is expected, improvements of up to 30% or more can be noted. Many attempts have been made to explain the nature of the placebo effect. Thus it has been suggested that a placebo acts by decreasing anxiety. Another explanation is that a placebo acts by meeting the expectations of the patient. It has also been proposed that the human placebo response has characteristics of a conditioned response.