[1] UCL, Res Dept Clin Educ & Hlth Psychol, London WC1E 7HB, England
[2] UCL, Div Psychiat, London WC1E 7HB, England
[3] North East London NHS Fdn Trust, Goodmayes Hosp, Ilford, England
[4] Univ E Anglia, Dept Clin Psychol, Norwich NR4 7TJ, Norfolk, England
[5] UCL, Dept Primary Care & Populat Hlth, London WC1E 7HB, England
[6] Univ London London Sch Econ & Polit Sci, Personal Social Serv Res Unit, London WC2A 2AE, England
[7] UCL, Dept Mental Hlth Sci, London WC1E 7HB, England