1. Department of Public Health and Primary Care, Leiden University Medical Center, Leiden, The Netherlands
2. Department of Child Health, TNO, Leiden, The Netherlands
3. Department of Youth Health Care, Centrum Jeugd en Gezin (Center for Youth and Family), The Hague, The Netherlands
4. Department of Epidemiology, Municipal Health Service The Hague (GGD Haaglanden), The Hague, The Netherlands