Understanding the placebo effect. Part 1: placebo use in clinical trials.

The concept of a placebo-what it is, what it does, and how it works-is very complex. In this article, I discuss some important aspects of the placebo effect on the basis of clinical research studies in pharmacology. The prevalence and magnitude of a placebo effect depend on how the clinical-placebo effect is measured, the characteristics of the condition being studied, and the experimental or clinical context in which the placebo is administered. Although the placebo effect is real, placebos are unlikely to work as effectively in real-world settings. Next month's article will describe important findings about the psychological and neurobiological processes that underlie the placebo effect.