Clustered Environments and Randomized Genes: A Fundamental Distinction between Conventional and Genetic Epidemiology

• George Davey Smith ,

  *To whom correspondence should be addressed. E-mail: george.davey-smith@bristol.ac.uk

  Affiliations Department of Social Medicine, University of Bristol, Bristol, United Kingdom , Medical Research Council Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom

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• Debbie A Lawlor,

  Affiliations Department of Social Medicine, University of Bristol, Bristol, United Kingdom , Medical Research Council Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom

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• Roger Harbord,

  Affiliation Department of Social Medicine, University of Bristol, Bristol, United Kingdom

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• Nic Timpson,

  Affiliations Department of Social Medicine, University of Bristol, Bristol, United Kingdom , Medical Research Council Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom

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• Ian Day,

  Affiliations Department of Social Medicine, University of Bristol, Bristol, United Kingdom , Medical Research Council Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom

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• Shah Ebrahim

  Affiliation Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom

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