[1] Kings Coll London, Dept Psychol, Inst Psychiat, London SE5 8AF, England
[2] Kings Coll London, Dept Mental Hlth Sci, London SE5 8AF, England
[3] Univ Manchester, Div Epidemiol & Hlth Sci, Biostat Grp, Manchester, Lancs, England
[4] Univ E Anglia, Sch Med Hlth Policy & Practice, Norwich NR4 7TJ, Norfolk, England