1. Division of Child Psychiatry, Department of Psychiatry, McMaster University, Child Epidemiology Unit, Chedoke Child and Family Centre, Hamilton, Ontario
2. Department of Psychiatry, McMaster University, Child Epidemiology Unit, Hamilton, Ontario.
3. Division of Child Psychiatry, Department of Psychiatry, University of Western Ontario, Child and Adolescent Centre, Victoria Hospital, London, Ontario
4. Child Epidemiology Unit, Hamilton, Ontario.