[1] Queen Mary Univ London, Barts & London Sch Med & Dent, Wolfson Inst Prevent Med, London, England
[2] Kings Coll London, Inst Psychiat, Dept Biostat, London, England
[3] Univ Cambridge, Inst Publ Hlth, Biostat Unit, MRC, Cambridge CB2 1TN, England
[4] MRC, Clin Trials Unit, London, England
[5] Kings Coll London, Acad Dept Psychol Med, London, England
[6] Univ Oxford, Dept Psychiat, Oxford OX1 2JD, England