[1] South African Med Res Council, Alcohol Tobacco & Other Drug Res Unit, Cape Town, South Africa
[2] Univ Cape Town, Dept Psychiat & Mental Hlth, Cape Town, South Africa
[3] Univ Cape Town, Dept Paediat & Child Hlth, Red Cross War Mem Childrens Hosp, Cape Town, South Africa
[4] Univ Cape Town, Div Epidemiol & Biostat, Sch Publ Hlth & Family Med, Cape Town, South Africa
[5] South African Med Res Council Unit Child & Adoles, Cape Town, South Africa
[6] South African Med Res Council Unit Anxiety & Stre, Cape Town, South Africa