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 f
|Contact: Julie O'Connor|
Wayne State University - Office of the Vice President for Research