1 Research Department, Crohn's and Colitis UK, Hatfield, United Kingdom.
2 St Mark's Hospital, Harrow, London, United Kingdom.
3 Division of Anaesthesia, Department of Medicine, University of Cambridge, Cambridge, United Kingdom.
4 Research Department of Clinical, Educational and Health Psychology, University College London, and Pain Management Centre, University College Hospitals NHS Foundation Trust, London, United Kingdom.
5 Division of Behavioral Medicine, Department of Medicine, University at Buffalo, SUNY, Buffalo, NY, United States.
6 Division of Care for Long-Term Conditions, Florence Nightingale Faculty of Nursing, Midwifery and Palliative Care, King's College, London, United Kingdom.
7 Primary Care Centre Versus Arthritis and Centre for Prognosis Research, Keele University, Keele, United Kingdom.