1. David J. DeWit is a research scientist in the Clinical, Social and Evaluation Research Department, Addiction Research Foundation, London, Ontario, Canada.
2. David R. Offord is the director of the Centre for Studies of Children at Risk, a professor of psychiatry, and the head of the Division of Child Psychiatry at McMaster University.
3. Maria Wong is a research associate in the Centre for Studies of Children at Risk, McMaster University.