[1] Australian Natl Univ, Natl Ctr Epidemiol & Populat Hlth, Canberra, ACT 0200, Australia
[2] Univ London, Ctr Psychiat, Wolf Inst Prevent Med, Barts & London,Queen Marys Sch Med & Dent, London EC1M 6BQ, England
[3] Univ Coll Med Sch, Ctr Paediat Epidemiol & Biostat, Inst Child Hlth, London WC1N 1EH, England