May C I van Schalkwyk , research fellow 1 , Pepita Barlow , assistant professor 3 , David Stuckler , professor of policy analysis and public management 4 , Maggie Rae , president 5 , Tim Lang , professor of food policy 6 , Tamara Hervey , Jean Monnet professor of European Union law 7 , Martin McKee , professor of European public health 1 1Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK 2Department of Health Policy, London School of Economics, London, UK 3Bennett Institute for Public Policy, University of Cambridge, Cambridge, UK 4Department of Policy Analysis and Public Management and Dondena Research Centre, University of Bocconi, Milan, Italy 5Faculty of Public Health, London, UK 6Centre for Food Policy, School of Health Sciences, City University of London, London, UK 7School of Law, University of Sheffield, Sheffield, UK Correspondence to: M C I van Schalkwyk may.vanschalkwyk{at}lshtm.ac.uk

Leaving the EU without a deal is a leap in the dark. May van Schalkwyk and colleagues call for a full evaluation of the health effects and suggest what it should cover

Key messages Leaving the EU without a deal threatens health and the NHS in many ways, but the scale of the threat remains unclear

We propose a framework that could be the basis for the comprehensive health impact assessment to inform politicians and the public

The government’s claims that it is prepared for no deal are implausible and, at best, might mitigate some of the worst consequences

Boris Johnson says that the UK will leave the EU on the 31 October 2019, “do or die.” Assuming he succeeds in this goal, the UK seems set to leave without a withdrawal agreement—a “no deal” scenario.

Health is central to Brexit. The Leave campaign claimed that Brexit would provide £350m ($390m; $430m) a week for the NHS and Johnson, on becoming prime minister, announced what he misleadingly described as “new” spending on the NHS. Thus, many people may think that a no deal Brexit will do no harm and could even be good for health and the NHS.

But will it? Two previous analyses have set out, in detail, why any form of Brexit will be damaging,12 and a leaked government document, written in early August 2019, paints an even more alarming picture.3 This contrasts starkly with the prime minister’s reassurances that the UK will “cope easily.”