Editors' introduction to 3rd thematic issue on philosophy of medicine.

Even though the evidence‐based medicine movement (EBM) labels mechanisms a low quality form of evidence, consideration of the mechanisms on which medicine relies, and the distinct roles that mechanisms might play in clinical practice, offers a number of insights into EBM itself. In this paper, I examine the connections between EBM and mechanisms from several angles. I diagnose what went wrong in two examples where mechanistic reasoning failed to generate accurate predictions for how a dysfunctional mechanism would respond to intervention. (...) I then use these examples to explain why we should expect this kind of mechanistic reasoning to fail in systematic ways, by situating these failures in terms of evolved complexity of the causal system(s) in question. I argue that there is still a different role in which mechanisms continue to figure as evidence in EBM: namely, in guiding the application of population‐level recommendations to individual patients. Thus, even though the evidence‐based movement rejects one role in which mechanistic reasoning serves as evidence, there are other evidentiary roles for mechanistic reasoning. This renders plausible the claims of some critics of evidencebased medicine who point to the ineliminable role of clinical experience. Clearly specifying the ways in which mechanisms and mechanistic reasoning can be involved in clinical practice frames the discussion about EBM and clinical experience in more fruitful terms. (shrink)

Cartwright and Munro argued that extrapolation of findings from randomized controlled trials to other settings can be difficult because information about the underlying causal structure and subgroups is often not available. They advocated the use of ‘capacities’ – that is fixed causal contributions – in predicting effects of interventions. In psychiatry, it is often not possible to determine what the fixed causal contributions are and one can only establish ‘approximate capacities’. However, using ‘approximate capacities’ does imply a different way of (...) evaluating health services, especially combined interventions. In health service research, if different studies, randomized controlled trials or other designs, have given different outcomes, the best way to investigate the effectiveness of a particular way of service organization is not to conduct more randomized controlled trials. It is preferable to study the effects of certain elements of the complex intervention, which have been tested before in other settings, that is investigating ‘approximate capacities’. One should check whether the separate elements do form a part of the complex intervention in practice and whether they have the same effect as in other studies and if not, why not. This enhances knowledge about the underlying causal structure and increases the possibility of extrapolation of the findings. (shrink)