[1] UCL, Inst Global Hlth, London WC1N 1EH, England
[2] London Sch Hyg & Trop Med, Maternal & Child Hlth Intervent Res Grp, London WC1E 7HT, England
[3] Human Dev Res Fdn, Islamabad 44000, Pakistan
[4] Umea Univ, Epidemiol & Global Hlth, S-90187 Umea, Sweden
[5] Univ Liverpool, Child Mental Hlth Unit, Inst Psychol Hlth & Soc, Liverpool L69 3BX, Merseyside, England
[6] London Sch Hyg & Trop Med, Dept Populat Hlth, London WC1E 7HT, England
[7] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, London WC1E 7HT, England
[8] London Sch Hyg & Trop Med, Hlth Econ & Syst Grp, London WC1E 7HT, England
[9] Univ Cape Town, Hlth Econ Unit, ZA-7925 Observatory, South Africa