1 IVO Addiction Research Institute, 2595 AA The Hague, The Netherlands. gera.nagelhout@maastrichtuniversity.nl.
2 Department of Health Promotion and Department of Family Medicine, Maastricht University (CAPHRI), 6200 MD Maastricht, The Netherlands. gera.nagelhout@maastrichtuniversity.nl.
3 Division of Health Promotion and Behavior, School of Public Health, Georgia State University, Atlanta, GA 30302, USA. lpopova1@gsu.edu.
4 Department of Public Health, Academic Medical Center, University of Amsterdam, 1100 DD Amsterdam, The Netherlands. m.a.kuipers@amc.uva.nl.