[1] Univ Oxford, Warneford Hosp, Dept Psychiat, Oxford OX3 7JX, England
[2] Univ Edinburgh, Dept Psychiat, Edinburgh EH8 9YL, Midlothian, Scotland
[3] Univ London London Sch Hyg & Trop Med, MRC, Trop Epidemiol Grp, London WC1E 7HT, England
[4] Univ Edinburgh, Western Gen Hosp, Canc Res UK Ctr, Edinburgh, Midlothian, Scotland
[5] Univ Edinburgh, Ctr Populat Hlth Sci, Edinburgh, Midlothian, Scotland