[1] St Georges Univ London, Populat Hlth Res Inst, Cranmer Terrace, London SW17 0RE, England
[2] Kings Coll London, Inst Psychiat Psychol & Neurosci, Hlth Serv & Populat Res Dept, De Crespigny Pk, London SE5 8AF, England
[3] Kings Coll London, Inst Psychiat Psychol & Neurosci, MRC Social Genet & Dev Psychiat Ctr, De Crespigny Pk, London SE5 8AF, England
[4] Imperial Coll London, Sch Publ Hlth, Imperial Clin Trials Unit, Stadium House,68 Wood Lane, London W12 7RH, England
[5] Univ Liverpool Liverpool Sch Trop Med, Dept Clin Sci, Pembroke Pl, Liverpool L3 5QA, Merseyside, England