Published on in Vol 17, No 1 (2015): January
1 Cancer Research UK Health Behaviour Research Centre, Department of Epidemiology and Public Health, University College London, London, United Kingdom
2 CAPHRI School for Public Health and Primary Care, Department of Family Medicine, Maastricht University Medical Centre, Maastricht, Netherlands
3 Centre for Outcomes Research and Effectiveness, Research Department of Clinical, Educational and Health Psychology, University College London, London, United Kingdom
4 Institute of General Practice, Medical Faculty of the Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
*these authors contributed equally