1. Aberdeen Health Psychology Group, University of Aberdeen, Aberdeen, UK
2. Health Services Research Unit, University of Aberdeen, Aberdeen, UK
3. Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa,Canada
4. School of Epidemiology and Public Health, University of Ottawa, Ottawa, Canada
5. School of Health Sciences, City University of London, London, UK
6. School of Health Sciences, University of Melbourne, Melbourne, Australia
7. Academic Unit of Primary Medical Care, University of Sheffield, Sheffield, UK
8. Institute of Applied Health Sciences, University of Aberdeen, Aberdeen, UK