Using the Stepfamily Genetic Design to Examine Gene-Environment Processes in Child and Family Functioning

Abstract

SUMMARY Studying children in different types of families-intact, single-mother, and stepparent families-affords opportunities for testing models of gene-environment processes, based on estimates of sibling similarity among full-siblings and half-siblings. We used a stepfamily quantitative genetic design to estimate genetic and environmental sources of variance in children's behavior problems and prosocial behaviors, as well as negativity in their relationships with their mothers and mothers' partners. Participants included full- and half-sibling pairs (same- and opposite-sex) from the Avon Longitudinal Study of Parents and Children. Mothers reported on their children's behavior problems and prosocial behaviors, as well as negativity in their parent-child relationships, for a target child (4 years old) and oneolder sibling (M =6.31 years). There was additive genetic variance in child behavior problems and partner-child negativity, and shared environmental variance in mother-child and partner-child negativity. One-fifth to two-thirds of the variance was accounted for by nonshared environment and error. These findings were similar even after controlling for sibling gender and age differences, the resident status of the older sibling, and the older siblings' degree of contact with the nonresident biological parent. The links between parental negativity and child behavior problems were mediated by genetic covariance suggesting possible gene-environment correlation processes, and the links between parental negativity and child prosocial behaviors were mediated primarily by environmental covariance.