Both nature and nurture appear to be significant factors in early antisocial behaviors of adopted children, a Wayne State University researcher believes.
Christopher Trentacosta, Ph.D., assistant professor of psychology in the College of Liberal Arts and Sciences, recently examined data from 361 linked triads (birth mother, adoptive parents, adopted child) in order to assess externalizing behavioral problems such as aggression and defiance when children were 18, 27 and 54 months of age.
The triads were part of the Early Growth and Development Study (EGDS), a nationwide, prospective study of birth parents and adoptive families that is supported by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute on Drug Abuse and the National Institute of Mental Health - all part of the National Institutes of Health - to Trentacosta's colleagues at the Oregon Social Learning Center and the Pennsylvania State University. The EGDS is aimed at investigating how families can help their children develop to their fullest potential.
In "Examining the Interplay of Birth Mothers' and Adoptive Parents' Antisocial Behavior in Predicting Growth in Externalizing Problems During Early Childhood," adoptive parents' antisocial behavior played an important role in the development of children's externalizing problems. His study was presented at the 2012 meeting of the Behavior Genetics Association in Edinburgh, Scotland.
That finding may not come as a surprise to researchers who have studied environmental precursors to such behavior. However, Trentacosta said a great deal of other research that examined sets of twins holds that genetic factors play a role as well.
Part of the problem with environmental studies, he said, is that the people providing the parenting are the same ones providing the genes. Using an adoption design, Trentacosta said, allows researchers to disentangle genetics from environmental influences by collecting data from both birth and adoptive parents.
His team found that adoptive parents reporting on their own antisocial behaviors predicted children's initial level of externalizing at 18 months, suggesting a direct environmental connection.
"That can be tricky, however, because it is those same parents reporting on the child's behavior," Trentacosta said, "so we aggregated both parents' reports to increase confidence somewhat. But even with the reporting limitation, there is something to be said for the environmental piece, at least initially."
His team's main finding is that there is an interaction between birth mother characteristics and adoptive parent antisocial behavior that is especially problematic for growth in externalizing behavior problems across early childhood.
"Compared to birth mothers with lower levels of antisocial behavior, children of birth mothers with higher levels of antisocial behavior showed steep growth in externalizing problems when raised by adoptive parents with higher levels of antisocial behavior," Trentacosta said. "Both genetic characteristics and environment matter, but it's especially the combination of the two that seems to make a difference over time."
Trentacosta believes further study of the next age group, 54 to 72 months, may help to better determine the most salient predictors of externalizing behavior levels by the time children reach school age.
Previous research has shown that such behaviors typically decrease across the preschool years and as children transition to elementary school. A logical next step, he said, would be to assess behavior levels from the cohort used in his work as the children get older to obtain a more complete picture of how genetic and environmental considerations play out across development.
"Behaviors that start out at fairly normative levels but still more than most can cause problems for children as they get to school age," Trentacosta said. "For prevention purposes, it's helpful if we can identify these children earlier and possibly get extra help for these families."