International adoption as a natural experiment.

International adoption research has been called a natural experiment by many child development researchers. How do studies of severe early deprivation inform us about risk factors experienced by many of these children and their impact on developmental outcomes? Three longitudinal studies conducted by British and American researchers in the 1990s are reviewed. Each year, over 20,000 children are adopted from overseas, and a significant number are now entering adolescence; the impact of their prenatal risk factors, early institutionalization, and ameliorative postadoptive environments is also reviewed. The feasibility of generalizing findings to other children in foster care is also addressed.