1. Institute of Health & Society, Newcastle University, The Baddiley-Clark Building, Richardson Road, Newcastle upon Tyne, UK
2. Institute of Epidemiology and Health Care, UCL, London, UK
3. Psychology & Human Development, Institute of Education, UCL, London, UK
4. Department of Epidemiology & Public Health UCL, London, UK
5. Population Health Research Institute, St George’s University of London, London, UK