Chapter

Evolutionary Thinking in Medicine

Part of the series Advances in the Evolutionary Analysis of Human Behaviour pp 357-369

Date:

The Ups and Downs of Placebos

  • Pete C. TrimmerAffiliated withSchool of Biological Sciences, University of Bristol Email author 
  • , Alasdair I. HoustonAffiliated withSchool of Biological Sciences, University of Bristol

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Abstract

We review the possible effects of placebos from an evolutionary perspective. Although the term ‘placebo effect’ has become synonymous with a good outcome, it is more useful to recognise that a placebo (i.e. a ‘dummy treatment’) may produce positive, neutral or negative outcomes. From this basis, we identify situations where evolutionary theory predicts that placebos should have positive or negative effects on patients, and how this will depend on numerous factors, such as age and health status. The evolutionary perspective highlights the many trade-offs involved in how the immune system can be affected by placebos, and the potential danger of confusing symptoms with an underlying ailment when considering effects.

Keywords

Natural selection Placebo Nocebo Expectation Belief Evolution