Evidence synthesis supports well-founded policymaking and public debate. The common question ‘What is the evidence for that?’ could be usefully rephrased as ‘Has sufficient synthesis of the evidence been done in relation to that?’. While typically asked in the former way, it is really the latter that is of interest.

Across disciplines and policy areas there are already good examples of evidence synthesis to inform policy and practice. These include the Oxford Martin Restatements (see case study 1) which review the natural science evidence on policy issues from bovine tuberculosis to ionizing radiation; Conservation Evidence which provides synthesised evidence relating to conservation interventions; Parliamentary Office for Science and Technology POST notes which succinctly summarise evidence to inform Parliamentary debate; and Evidence Aid which promotes the use of evidence in the humanitarian sector. Cochrane also provides synthesised evidence to inform specific healthcare decisions, and the Campbell Collaboration provides a similar service for decision-making in education, social welfare, crime and justice, and international development. For the past two decades the UK Government has been using evidence synthesis to inform policy development and implementation across departments and sectors.

Despite this good practice, there are significant challenges associated with moving to a world in which high-quality synthesised evidence is routinely available across all areas of policy and science. Because evidence synthesis for policy sits at the interface of public life and academia, meeting these challenges will require collaboration between researchers, policymakers, practitioners, funders and publishers. Sustained and effective communication and brokerage between these communities will be essential. This document from the Royal Society and Academy of Medical Sciences outlines the case for evidence synthesis. It then proposes a set of principles that defines the fundamental features of good synthesis. Finally, it proposes changes to the research and policy landscapes that would create a more effective ‘marketplace’ for synthesis: one in which policymakers and commentators reach out to where accessible and timely evidence is available, and one in which researchers are engaged in synthesising evidence because they know it will make a difference.

This document reflects discussions at two meetings organised by the Royal Society and Academy of Medical Sciences in 2017, and draws on expertise from a range of disciplines including medicine, natural sciences, social sciences and international development.