[1] Newcastle Univ, Inst Cellular Med, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[2] Royal Hosp Sick Children, Dept Paediat, Edinburgh EH9 1LF, Midlothian, Scotland
[3] Royal Hosp Sick Children, Dept Paediat Gastroenterol, Glasgow G3 8SJ, Lanark, Scotland
[4] Newcastle Univ, Inst Hlth & Soc, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[5] Newcastle Tyne Hosp NHS Trust, Paediat Immunol & Infect Dis Dept, Newcastle Upon Tyne, Tyne & Wear, England
[6] UCL, Inst Child Hlth, London, England
[7] Newcastle & N Tyneside NHS Trust, Dept Hlth Psychol, Newcastle Upon Tyne, Tyne & Wear, England
[8] Great Ormond St Hosp Sick Children, Dept Psychosocial Serv, London WC1N 3JH, England