Infant domestic adoption: outcomes at mid-life.

Background: Adoption studies can cast light on environmental influences on development, but heterogeneity in preplacement experiences often complicates interpretation of findings.

Methods: We studied infant-adopted samples drawn from the 1958 and 1970 British birth cohorts and examined mental health, well-being, physical health and externalizing outcomes at mid-life. Outcomes for adopted cohort members were compared with those of (a) individuals raised in two biological parent families ('general population' comparisons) and (b) birth comparison groups of other nonadopted children from similar circumstances at birth.

Results: In both cohorts, to-be-adopted children shared early characteristics in common with birth comparison children, but were placed in more socially advantaged adoptive homes. Followed to mid-life, there were few group differences on indicators of physical health or psychological well-being. Levels of psychological distress were comparable in the adopted and general population samples in both cohorts, and more favourable than in the birth comparison groups among women in the 1958 cohort; more beneficial childhood family circumstances contributed to these differences. Rates of adult externalizing outcomes were comparable in the adopted and birth comparison groups in both cohorts, and higher than in the general population samples; indicators of maternal and prenatal exposures contributed to these differences.

Conclusions: Rearing in adoptive homes may provide protective effects in relation to internalizing problems but may not be as protective in relation to externalizing outcomes.