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  1. Rebecca Y. Steer,
  2. Emory University,
  3. Lorie A. Ritschel

Published Online: 30 JAN 2010

DOI: 10.1002/9780470479216.corpsy0687

Corsini Encyclopedia of Psychology

Corsini Encyclopedia of Psychology

How to Cite

Steer, R. Y., University, E. and Ritschel, L. A. 2010. Placebo. Corsini Encyclopedia of Psychology. 1–2.

Author Information

  1. Emory University School of Medicine

Publication History

  1. Published Online: 30 JAN 2010


A placebo is a substance that has little or no active pharmacological effect on the symptoms for which it is administered. The placebo effect occurs when inert substances, such as sugar pills, are given in place of active medications and the recipient's condition changes in the desired direction. Placebo treatments may also include the prescription of substances with known physiological effects but a mechanism of action that is unrelated to the patient's presenting problem (e.g., prescribing vitamins for a chronic pain condition). In this case, the placebo is given with the hope of promoting improved health through increased positive expectancies on the part of the patient. Because the recipient is not aware of the inactive nature of the placebo, the observed changes are often attributed to positive expectations about the treatment.


  • placebo;
  • placebo effect;
  • placebo treatment;
  • expectancy;
  • demand effects