[1] Weill Cornell Med Coll, Hamad Gen Hosp, Hamad Med Corp, Dept Med Stat & Epidemiol,Dept Publ Hlth, Doha, Qatar
[2] Univ Manchester, Sch Epidemiol & Hlth Sci, Dept Evidence Populat Hlth Unit, Manchester, Lancs, England
[3] Hamad Med Corp, Dept Psychiat, Doha, Qatar
[4] St Georges Univ London Cranmer Terrace, Head Addict Res Grp, Deputy Head Div Mental Hlth, London, England