Development

The consensus among researchers is that adoption affects development throughout life, with the fact of "being adopted," creating unique responses to significant life-events, e.g., the birth of a child. As a result, researchers often assume that the adoptee population faces heightened risk in terms of psychological development and social relationships. Earlier literature on the topic supported the conception of such problems, however, much of that research has since been deemed flawed due to methodological failures.[110]

Some conclusions about the development of adoptees can be gleaned from newer studies, though, and it can be said that adoptees, in some respect, seem to develop differently than the general population while facing greater risks during adolescence.

Concerning developmental milestones, studies from the Colorado Adoption Project examined genetic influences on adoptee maturation, concluding that cognitive abilities of adoptees reflect those of their adoptive parents in early childhood but show little similarity by adolescence, resembling instead those of their biological parents and to the same extent as peers in non-adoptive families.[111]

Similar mechanisms appear to be at work in the physical development of adoptees. Danish and American researchers conducting studies on the genetic contribution to body mass index found correlations between an adoptee's weight class and his biological parents' BMI while finding no relationship with the adoptive family environment. Moreover, about one-half of inter-individual differences were due to individual non-shared influences.[112][113]

These differences in development appear to play out in the way young adoptees deal with major life events. In the case of parental divorce, adoptees have been found to respond differently than children who have not been adopted. While the general population experienced more behavioral problems, substance use, lower school achievement, and impaired social competence after parental divorce, the adoptee population appeared to be unaffected in terms of their outside relationships, specifically in their school or social abilities.[114]

The adoptee population does, however, seem to be more at risk for certain behavioral issues. Researchers from the University of Minnesota studied adolescents who had been adopted and found that adoptees were twice as likely as non-adopted people to suffer from oppositional defiant disorder and attention-deficit/hyperactivity disorder (with an 8% rate in the general population).[115] Suicide risks were also significantly greater than the general population. Swedish researchers found both international and domestic adoptees undertook suicide at much higher rates than non-adopted peers; with international adoptees and female international adoptees, in particular, at highest risk.[116]

Nevertheless, work on adult adoptees has found that the additional risks faced by adoptees are largely confined to adolescence. Young adult adoptees were shown to be alike with adults from biological families and scored better than adults raised in alternative family types including single parent and step-families.[117] Moreover, while adult adoptees showed more variability than their non-adopted peers on a range of psychosocial measures, adult adoptees exhibited more similarities than differences with adults who had not been adopted.[118]