Don't discount the placebo

Abstract: Physicians have long known that patients may respond to placebo (objectively inert) treatments.  Socrates noted that:
[The cure for a headache] was a kind of leaf, which required be accompanied by a charm, and if a person would repeat the charm at the same time that he used the cure, he would be made whole; but that without the charm the leaf would be of no avail. (Plato, Charmides, 380 BC).

In this seminar I will discuss three mechanisms that might contribute to placebo effects in clinical trials: regression to the mean; subject expectancy specific to the trial setting (Hawthorne Effect); and subject expectancy generalisable to routine practice (true placebo effect).  I will then illustrate the potential influence of different assumptions as to the underlying mechanisms of a placebo effect on cost-effectiveness estimates and adoption decisions.  Finally, I will consider the implications for the conduct of cost-effectiveness analyses.