Mechanisms of placebo and placebo-related effects across diseases and treatments

Annu Rev Pharmacol Toxicol. 2008;48:33-60. doi: 10.1146/annurev.pharmtox.48.113006.094711.


The placebo effect has evolved from being thought of as a nuisance in clinical and pharmacological research to a biological phenomenon worthy of scientific investigation in its own right. It is now clear that the term placebo effect is too restrictive and, in fact, many placebo-related effects have recently been investigated. A placebo effect differs from a placebo-like effect in that the former follows the administration of a placebo, whereas in the latter no placebo is administered. However, in both cases, the psychosocial context around the treatment plays a key role. In recent years, placebo and placebo-related effects have been analyzed with sophisticated biological tools that have uncovered specific mechanisms at both the biochemical and cellular level. This recent research has revealed that these psychosocial-induced biochemical changes in a patient's brain and body in turn may affect the course of a disease and the response to a therapy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Cognition / physiology
  • Conditioning, Classical / physiology
  • Humans
  • Placebo Effect*
  • Placebos*
  • Research Design*


  • Placebos