1. Division of Adolescent and Young Adult Medicine, Department of Pediatrics, University of California, San Francisco, San Francisco, California, USA.
2. Center for Health Sciences, SRI International, Menlo Park, California, USA.
3. Factor-Inwentash Faculty of Social Work, University of Toronto, Toronto, Ontario, Canada.
4. Department of Management, Policy and Community Health, University of Texas Health Science Center at Houston, Houston, Texas, USA.
5. Department of Population, Family, and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA.
6. School of Physiology, University of the Witwatersrand, Johannesburg, South Africa.