1. Alcohol, Tobacco and Other Drug Research Unit, South African Medical Research Council, Cape Town, South Africa;
2. Department of Psychiatry and Mental Health, University of Cape Town, Cape Town, South Africa;
3. School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa;
4. School of Public Health, University of the Witwatersrand, Johannesburg, South Africa;
5. Department of Psychiatry, Stellenbosch University, Cape Town, South Africa