However international medical science has become, communicating electronically at the speed of light, some fields are still worlds apart. The movement that is subsumed under the banner of evidence based medicine, with its sister movements such as the Cochrane Collaboration or the BMJ's Clinical Evidence, aims to evaluate whether the benefits of treatments that had been hoped for actually exist. This relies almost exclusively on randomised controlled trials, in particular in the study of drug interventions. In a world apart is the field of pharmacoepidemiology, devoting itself mainly to detection and systematic studies of the adverse effects of the very same treatments. Adverse drug effects are often unanticipated and are predominantly investigated by observational studies—for example, by using large databases that link routine prescriptions with the occurrence of unexpected disease.

The protagonists of these fields barely know each other: they publish in different journals, write and read different books, and work in different departments. They are even suspicious of each other's methods. Adepts of evidence based medicine doubt …