An appeal to EBM to expand the notion of evidence

November 20, 2018 Jon Williamson

BMJ Evidence-Based Medicine has published an appeal from the research groups CauseHealth, EBM+ and PhilPharm, as well as other researchers, to broaden the evidence base considered by evidence-based medicine.


In particular, the signatories maintain that:

“Establishing causation often requires the use of multiple methods since no single method will be universally applicable or perfect for this purpose. This means that statistical approaches, in particular randomised controlled trials and systematic reviews, cannot uncover all causally relevant information, contrary to their widespread assumed status as the universal gold standards of EBM.

An understanding of causal mechanisms can help to determine whether an intervention works (ie, its efficacy shown in experiment or effectiveness in clinical practice).”


If this is right, then evidence of mechanisms should be treated on a par with clinical studies. In contrast, present-day EBM often takes evidence of mechanisms to be inferior to clinical studies, as shown in the above evidence hierarchy, which is used by SUNY for EBM training.

Jon Williamson
University of Kent