1. Alcohol & Drug Abuse Research Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg 7505, South Africa
2. Biostatistics Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg 7505, South Africa
3. Statistics and Population Studies Department, University of the Western Cape, P.O. Box X17, Bellville 7535, South Africa
4. Health Systems Research Unit, South African Medical Research Council, P.O. Box 19070, Tygerberg 7505, South Africa
5. Women’s Health Research Unit, School of Public Health and Family Medicine, University of Cape Town, Falmouth Building, Medical Campus, Observatory 7925, South Africa
6. Department of Psychiatry, Stellenbosch University, P.O. Box 19063, Tygerberg 7505, South Africa