[1] Univ Sheffield, Sch Hlth & Related Res ScHARR, Sheffield S1 4DP, S Yorkshire, England
[2] Northern Gen Hosp, Sheffield Adult CF Ctr, Sheffield, S Yorkshire, England
[3] Kings Coll London, Dept Psychol, Inst Psychiat Psychol & Neurosci IoPPN, London, England
[4] Sheffield Hallam Univ, Ctr Behav Sci & Appl Psychol CeBSAP, Sheffield, S Yorkshire, England
[5] Univ Sheffield, Sheffield Clin Trials Res Unit CTRU, Sheffield, S Yorkshire, England
[6] Nottingham Univ Hosp NHS Trust, Dept Resp Med, Wolfson Cyst Fibrosis Ctr, Nottingham, England