1. Department of Medicine; University of California San Diego; La Jolla CA USA
2. School of Population Health Sciences; King's College London, Addison House, Guy's Campus; London UK
3. Behaviours and Health Risks Program; Burnet Institute; Melbourne Victoria Australia
4. School of Public Health and Preventive Medicine; Monash University; Melbourne Victoria Australia
5. British Columbia Centre on Substance Use; Vancouver BC Canada
6. Division of AIDS, Department of Medicine; University of British Columbia; Vancouver BC Canada
7. International Centre for Science in Drug Policy, St Michael's Hospital; Toronto ON Canada