BMJ  2008;336:1086 (17 May), doi:10.1136/bmj.39577.518009.3A

Letters

Placebo effect

Reconceptualising placebo

The first 150 words of the full text of this article appear below.

The notion that placebo responses are responses that are evoked by nothing is nonsense. The study by Kaptchuk et al and the study by Waber et al in JAMA illustrate clearly that the "placebo"’ responses observed are in fact responses to things other than the thing to which we hypothesise a response.^{1 2} Therefore, placebo responses reflect the limitations of our experimental design, our appreciation of the contributors to a patient’s symptoms, and our appreciation of what might change those underpinning factors. The convincing placebo data concern symptoms—experiences reported by patients. That means that symptoms are outputs of the brain. That a placebo response occurs means that something has changed the brain’s evaluation of whether or not to evoke that symptom. This makes a placebo response not a response to nothing, but to something we haven’t identified or measured. Take pain for example: it emerges according to an implicit evaluation of . . . [Full text of this article]

¹ University of Oxford, Oxford OX1 3QX

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