As medical knowledge accumulates, the number of placebo trials should fall

When an effective treatment exists and then a new one comes along it is only common sense to ask whether the new treatment beats the old. As Bradford Hill suggested, who cares whether the new treatment is more or less effective than nothing?1Despite this common sense, the dogma persists that placebo control is part of the paradigm for evaluating new treatments. For example, Collier recently claimed that “placebo controlled trials offer the greatest scientific rigour for assessing the efficacy of a drug,”2 and Jones et al in this issue (p 36), write that “the gold standard in clinical research is the randomised placebo controlled double blind clinical trial.”3

Placebo control should no longer be part of the gold standard. In earlier times it made sense to urge investigators to compare new treatments with placebo, because typically the only alternative to the new treatment was no effective treatment at all. Introducing a placebo facilitated blind assessment and controlled for non-specific aspects of treatment–the “placebo” effect, itself a highly variable but often powerful phenomenon.4 But if blind assessment can be achieved in a …