Birth Complications and Negative Emotionality Predict Externalizing Behaviors in Young Twins: Moderations with Genetic and Family Risk Factors.

We examined interactions among genetic, biological, and ecological variables predicting externalizing behaviors in preschool and middle childhood. Specifically, we examined prediction of externalizing behaviors from birth complications and negative emotionality, each moderated by genetic risk for aggression and ecological risk factors of insensitive parenting and low family income. At ages 4 and 5 years, 170 twin pairs and 5 triplet sets (N = 355 children) were tested; 166 of those children were tested again at middle childhood (M = 7.9 years). Multilevel linear modeling results showed generally that children at high genetic risk for aggression or from low-income families were likely to have high scores on externalizing, but for children not at high risk, those with increased birth complications or more negative emotionality had high scores on externalizing. This study underscores the importance of considering biological variables as moderated by both genetic and ecological variables as they predict externalizing behaviors across early childhood.