Causal diagrams, the placebo effect, and the expectation effect

Eyal Shahar, Doron J. Shahar

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Using causal diagrams, a formal research methodology, we analyzed several definitions of placebo and the placebo effect. We conclude that placebo is an ambiguous, redundant term and that the so-called placebo effect conceals far more interesting effects that are attributed to the patient's expectation. Biomedical research will benefit from abandoning the term placebo effect and focusing instead on a deeper understanding of the expectation variable, including its causes, effects, and effect modifiers. This avenue of research should be pursued by observational cohorts that are nested within clinical trials.

Original languageEnglish (US)
Pages (from-to)821-828
Number of pages8
JournalInternational Journal of General Medicine
StatePublished - 2013


  • Causal diagrams
  • Effect modification
  • Expectation
  • Placebo

ASJC Scopus subject areas

  • General Medicine


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