1. Department of Child Psychiatry University of Turku Turku Finland
2. Department of Adolescent Psychiatry University of Helsinki and Helsinki University Central Hospital Helsinki Finland
3. Welfare Department National Institute for Health and Welfare Helsinki Finland
4. Department of Biostatistics Columbia University Mailman School of Public Health New York New York USA
5. Department of Child Psychiatry Turku University Central Hospital Turku Finland
6. Department of Psychiatry College of Physicians and Surgeons of Columbia University and New York State Psychiatric Institute New York New York USA
7. Department of Epidemiology Columbia University Mailman School of Public Health New York New York USA