Pain Research, Nuffield Department of Anaesthetics, University of Oxford, Oxford Radcliffe Hospital, The Churchill, Oxford OX3 7LJ, UK. henry.mcquay@pru.ox.ac.uk
Placebo, used here to mean an inert treatment given as if it was a real treatment, means lots of different things to different people. The structure of the article is that it begins by talking about the technical use of placebos in clinical trials, and the extent of the placebo response, then about the mechanism--"How does the placebo work?"--and last about the ethics of placebo in the contexts of research and in everyday practice.