About the Authors

Mark Petticrew

mark.petticrew@lshtm.ac.uk

Affiliation Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom

George Davey Smith

Affiliation Centre for Causal Analyses in Translational Epidemiology (CAiTE), School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: MP GDS. Performed the experiments: MP GDS. Analyzed the data: MP GDS. Wrote the paper: MP GDS.