title: Placebo: misunderstandings and prejudices.
abstract: BACKGROUND
  The role of placebos is often misunderstood, leading both to overvaluation and to inappropriate disdain. The effect of a placebo that contains no pharmacologically active substance is often confused with the effect of administration by a physician. The aim of this article is to review the current data on placebos, evaluate these data critically, and provide a well-founded and understandable explanation of the effects that placebos do and do not possess.
  
  
  METHODS
  Selective literature review.
  
  
  RESULTS
  Recent studies employing modern imaging techniques have provided objective correlates of the effect of placebo administration for certain indications. A recent paper even suggested a genetic basis for it. Two main mechanisms underlie the effect of placebo administration: conditioned reflexes, which are subconscious, and the patient's expectations, which are conscious. Further factors include the physician's personality and the setting in which the treatment takes place.
  
  
  CONCLUSIONS
  The mechanisms of action of placebo administration, with which positive therapeutic effects can be achieved with little effort, should be consciously exploited by physicians when giving their patients pharmacologically active medications as well.
authors.affiliation: Medizinische Klinik I, Kliniken im Naturpark Altmühltal, Klinik Kösching Krankenhausstr. 19 85092 Kösching, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Breidert
authors.forename: Karl
authors.initials: K
authors.lastname: Hofbauer
mesh_terms: D002986:Clinical Trials as Topic; D003213:Conditioning, Psychological; D017060:Patient Satisfaction; D015990:Placebo Effect; D011287:Prejudice; D012718:Set, Psychology