Natural experiments have long been used as opportunities to evaluate the health impacts of policies, programmes, and other interventions. Defined in the UK Medical Research Council’s guidance as events outside the control of researchers that divide populations into exposed and unexposed groups, natural experiments have greatly contributed to the evidence base for tobacco and air pollution control, suicide prevention, and other important areas of public health policy.1Although randomised controlled trials are often viewed as the best source of evidence because they have less risk of bias, reliance on them as the only source of credible evidence has begun to shift for several reasons. Firstly, policy makers are increasingly looking for evidence about “what works” to tackle pervasive and complex problems, including the social determinants of health,23 and these are hard to examine in randomised trials. In Scotland, for example, legislation to introduce a minimum retail price per unit of alcohol…

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