1. Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust , Bradford, West Yorkshire, UK
2. Faculty of Health Studies, University of Bradford , Bradford, West Yorkshire, UK
3. School of Psychology, University of Leeds , Leeds, West Yorkshire, UK
4. MRC Integrative Epidemiology Unit, University of Bristol , Clifton, Bristol, UK
5. Bristol Medical School, University of Bristol , Clifton, Bristol, UK
6. Department of Health Sciences, University of York , York, West Yorkshire, UK