Published on in Vol 18, No 9 (2016): September
1 Cambridge Centre for Health Services Research, University of Cambridge, Cambridge, United Kingdom
2 Manchester Centre for Health Psychology, University of Manchester, Manchester, United Kingdom
3 The Psychometrics Centre, University of Cambridge, Cambridge, United Kingdom
4 Centre for Primary Care, University of Manchester, Manchester, United Kingdom
5 School of Nursing, Midwifery and Social Work, University of Manchester, Manchester, United Kingdom
6 Collaboration for Academic Primary Care, University of Exeter, Exeter, United Kingdom
*all authors contributed equally