CONCEPT OF TRUE AND PERCEIVED PLACEBO-EFFECTS

We often and wrongly equate the response seen in the placebo arm of a clinical trial with the placebo effect. In order to obtain the true pl acebo effect, other non-specific effects can be identified by includin g an untreated control group in clinical trials. A review of the liter ature shows that most authors confuse the perceived placebo effect wit h the true placebo effect. The true placebo effect is highly variable, depending on several factors that are not fully understood. A distinc tion between the perceived and the true placebo effects would be helpf ul in understanding the complex phenomena involved in a placebo respon se.