1. Norwegian Institute of Public Health; Division for Health Services; PO Box 4404 Nydalen Oslo Norway 0403
2. Regional Centre for Child and Adolescent Mental Health, Eastern and Southern Norway (RBUP); RBUP, Postboks 4623 Nydalen Oslo Norway 0405
3. University of Oslo; Faculty of Medicine; Oslo Norway
4. London School of Hygiene & Tropical Medicine; Department of Clinical Research; Keppel Street London UK WC1E 7HT