Childhood problem behavior and parental divorce: evidence for gene–environment interaction

The importance of genetic and environmental influences on children’s behavioral and emotional problems may vary as a function
of environmental exposure. We previously reported that 12-year-olds with divorced parents showed more internalizing and externalizing
problems than children with married parents, and that externalizing problems in girls precede and predict later parental divorce.
The aim of the current study was to investigate as to whether genetic and environmental influences on internalizing and externalizing
problems were different for children from divorced versus non-divorced families.

Maternal ratings on internalizing and externalizing problems were collected with the Child Behavior Checklist in 4,592 twin
pairs at ages 3 and 12 years, of whom 367 pairs had experienced a parental divorce between these ages. Variance in internalizing
and externalizing problems at ages 3 and 12 was analyzed with biometric models in which additive genetic and environmental
effects were allowed to depend on parental divorce and sex. A difference in the contribution of genetic and environmental
influences between divorced and non-divorced groups would constitute evidence for gene–environment interaction.

For both pre- and post-divorce internalizing and externalizing problems, the total variances were larger for children from
divorced families, which was mainly due to higher environmental variances. As a consequence, heritabilities were lower for
children from divorced families, and the relative contributions of environmental influences were higher.

Environmental influences become more important in explaining variation in children’s problem behaviors in the context of parental
divorce.