Gene-Environment Interactions in the Association Between Harsh Parenting and Child Aggression

Background and Purpose: This study used the Fragile Families and Child Well-Being Study to examine the association of harsh parenting and child aggression across the first decade of life. We also explored moderating processes that cut across the child’s ecology, from a broad cumulative ecological risk index to more proximal individual genetic differences in the dopaminergic system potentially indicative of greater sensitivity to environmental influences.

Methods: Maternal report of harsh parenting, defined as high frequency spanking, was assessed at age 1, 3, 5 and 9, along with child externalizing behavior at age 9 (N=2,768). The longitudinal study allowed for a breadth of environmental and individual variables to be included in a cumulative risk index capturing 16 ecological risk factors. We were also able to examine child genetic polymorphisms across four genes involved in the dopaminergic system (DRD2, DRD4, DAT1, and COMT) to create a cumulative count of sensitive risk alleles.

Results: Examining the moderating effects of cumulative risk on the association between harsh parenting and externalizing we found significant main effects for both cumulative risk (F(2, 2731)=31.06, p<.001) and harsh parenting (F(2, 2731)=36.88, p<.001). Controlling for gender, race, maternal nativity, and city of residence, we found cumulative risk significantly moderate the effects of harsh parenting on externalizing (Interaction: F(4, 2731)=3.24, p=.01), with the effects of spanking being amplified for those experiencing greater levels of risk. In the second set of analyses, examining the effects of a cumulative count of sensitive alleles, again controlling for gender, race, city of residence, and a cumulative risk index score, we found a significant main effect for the experience of early harsh parenting on age 9 externalizing behavior (F(1, 2352) = 4.3, p < .05), with a significant interaction between harsh parenting and genetic profile (F(2, 2352)=3.77, p<.05), such that the association between harsh parenting and downstream aggression was strengthened with higher number of sensitive alleles.

Conclusions and Implications: The data underscore the high levels of frequent spanking with nearly one in five of the children experiencing frequent spanking for at least one of the four assessment waves at ages 1, 3, 5 or 9. Of particular concern, 6% of children experienced this marker of harsh parenting at two or more assessment waves. Complicating the experiences of children receiving harsh parenting was the high level of cumulative ecological risk families were experiencing with 27% experiencing 6 or more risks. The accumulation of risk not only predicts greater reliance on harsh parenting, it also appears to moderate the downstream behavioral outcomes associated and leaves children more sensitive to the effects of such parenting. We also find evidence for a moderating role for individual differences in the genetic profiles of the dopaminergic systems of children indicative of greater sensitivity to parenting harshness for some children. Harsh parenting, in the form of high frequency spanking, remains a too common experience for children, and results demonstrate that the effects of exposure are amplified for those children already facing the most burden and those more biologically sensitive to parenting harshness.