Harvard Mental Health Letter

Reconsidering the placebo response

In scientific studies, the term placebo usually refers to an inert pill or procedure that serves as a comparison to an active intervention (typically a drug or psychotherapy). Now a handful of acupuncture studies not only provides additional evidence that a placebo itself can have dramatic impact on illness, but also suggest that the context in which an intervention takes place can bolster the placebo response. The nature of the placebo response — and whether it even exists — has been the subject of scientific discussion for decades. In a 1955 paper, pioneering anesthesiologist Dr. Henry K. Beecher famously described the placebo response as powerful. Nearly a half-century later, a review published by the prestigious Cochrane Collaboration concluded instead that the placebo might be powerless. More recently, the Cochrane reviewers conducted another analysis and reached a middle ground, concluding that for some clinical conditions — particularly pain and nausea — placebos may confer symptom alleviation, while in other situations they do not. This raises the obvious question: why would placebos work in some cases but not in others? The latest research has been aimed at better understanding the placebo response by studying it on its own rather than just as a comparison to a drug or psychotherapy.
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