Letters Placebo effect

Reconceptualising placebo

BMJ 2008; 336 doi: http://dx.doi.org/10.1136/bmj.39577.518009.3A (Published 15 May 2008) Cite this as: BMJ 2008;336:1086
  1. G Lorimer Moseley, Nuffield medical research fellow
  1. 1University of Oxford, Oxford OX1 3QX
  1. lorimer.moseley{at}medsci.ox.ac.uk

    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 the threat to body tissue and the need for action. It is sensible that anything that changes this implicit evaluation of threat should change pain.

    Rather than interpreting “placebo” responses as mysterious unexplainable responses to nothing, we should, as the editorial hints,3 get excited about what else might have led the patient’s brain to conclude that the need for symptoms had just reduced. To suggest we should use the placebo response in clinical practice seems a bit daft to me because it is the other things (we are yet to identify, accept, or understand), which change the brain’s evaluation of the need for symptoms, that we should utilise. I agree that the alternative therapies are way in front of us here—they know they are using some of these things, it just doesn’t make them conclude that what they do is useless.


    • Competing interests: None declared.