Data were gathered during the course of the Christchurch Health and Development Study, a longitudinal study of a birth cohort of 1,265 New Zealand children born in Christchurch in mid-1977. The children were tracked from birth through the age of 16. In all cases, children who were adopted were born to single mothers who placed their children for adoption. Findings also reveal that the social background of adoptive families and childhood circumstances of adoptees were not significantly different from those of children who entered biological two-parent families. However, the environmental advantages experienced by children who entered adoptive families were not directly reflected in the pattern of adolescent adjustment in this group.
Researchers conclude that increased rates of externalizing behaviors is due to genetic background.
The findings suggest that adoptive children may have been a biologically high risk group for externalizing behaviors but that the generally advantaged childhood they received in the adoptive family may have mitigated the risk somewhat with the result that adoptive children had risks of problem behaviors that were somewhere between the elevated risks of children of similar biological background and the lower risks of children with similar social background. A 16-Year Longitudinal Study. 1995 Journal of Child Psychology and Psychiatry. A second article reviews the findings of 2 studies which surveyed adoptive families drawn from large population studies, thus reducing chances of a biased sample. Data from the NCDS were used to examine predictors of attainment among adoptees, nonadopted children from similar birth circumstances, and other members of this national birth cohort over a 40 year period.