title: The nature and ethics of natural experiments.
abstract: Natural experiments are an important methodology often used to answer research questions that would, otherwise, be impossible to address, or employed because of ethical concerns about the use of randomisation to interventions that carry known risks. The UK Medical Research Council (MRC) recently produced an extremely useful document discussing the nature and significance of natural experiments within medical and public health research. In this paper, however, we suggest that the MRC document's definition of the term 'natural experiment' is insufficiently precise. In response, we offer a taxonomy of different types of natural experiments and related methods, and explore the ethical implications of these different types. We argue that while the ethical issues that may arise within natural experiments in relation to risks of harm or informed consent may differ from those within the randomised controlled trial, they are not thereby less pressing. The implications of the argument are explored and recommendations made for those involved in research governance.
authors.affiliation: Centre for Values, Ethics and the Law in Medicine (VELiM), School of Public Health, University of Sydney, Sydney, Australia.
authors.forename: Angus
authors.initials: A
authors.lastname: Dawson
authors.affiliation: Arthritis Research UK Primary Care Centre, Institute for Primary Care and Health Sciences, Keele University, Staffordshire, UK.
authors.forename: Julius
authors.initials: J
authors.lastname: Sim
mesh_terms: D035843:Biomedical Research / Q000941:ethics*; D004992:Ethics, Medical; D032984:Ethics, Research; D006801:Humans; D007258:Informed Consent / Q000941:ethics; D011634:Public Health; D006113:United Kingdom
keywords: Informed Consent; Research Ethics