The rapid dominance of evidence-based medicine has sparked a philosophical debate concerning the concept of evidence. We urge that evidence-based medicine, if it is to be practised in accordance with its own mandate, should also acknowledge the importance of understanding causal mechanisms.1–7 The undersigned include 42 clinicians and philosophers from interdisciplinary research networks working specifically on questions related to causation in medicine worldwide. 

Our research has developed out of a conviction that philosophical analysis ought to have a direct impact on the practice of medicine. In particular, if we are to understand what is meant by ‘evidence’, what is the ‘best available evidence’ and how to apply it in the context of medicine, we need to tackle the problem of causation head on.1 8–12 In practice, this means understanding the context in which evidence is obtained, as well as how the evidence might be interpreted and applied when making practical clinical decisions.7 13 It also means being explicit about what kind of causal knowledge can be gained through various research methods. The possibility that mechanistic and other types of evidence can be used to add value or initiate a causal claim should not be ignored.3–7 14 15 This appeal for a broader approach to evidence is also important to patients, who need clear information on the benefits and harms of medicines.16

We have arrived at several overlapping conclusions with implications for policy and practice in research and clinical care, which we summarise briefly:

1. ‘Evidence’ is typically evidence of causation. Common terms used in EBM, such as ‘intervention’, ‘outcome’ or ‘increased risk’, are relevant to evidence-based decision-making only insofar as they point to causal matters: causal interventions and their effects. Although there is growing …