[1] London Sch Econ & Polit Sci, Personal Social Serv Res Unit, London WC2A 2AE, England
[2] Kings Coll London, Inst Psychiat, Ctr Econ Mental & Phys Hlth, London SE5 8AF, England
[3] UCL, Dept Stat Sci, London WC1E 6BT, England
[4] UCL, PRIMENT Clin Trials Unit, London WC1E 6BT, England
[5] Royal Free Hosp, Inst Epidemiol & Hlth, London NW3 2PF, England
[6] Camden & Islington NHS Fdn Trust, London N19 4PJ, England
[7] UCL, Mental Hlth Sci Unit, London W1W 7EJ, England