1. Department of Clinical and Biological Sciences, University of Torino, Orbassano, Torino, Italy
2. Piedmont Centre for Drug Addiction Epidemiology, Grugliasco, Torino, Italy
3. United Nations Office on Drugs and Crime, Project Office, Lagos, Nigeria
4. University of Jos, Jos, Nigeria
5. Faculty of Education, Health and Social Work, University College Ghent, Ghent, Belgium