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Children’s aggressive behavior may contribute to parents becoming less consistent with discipline, rather than inconsistent discipline simply causing children to become more aggressive, according to research published in Nature Communications. The study also found that shared genes explained part of the link between inconsistent discipline and aggression, and all of the link between positive parenting and lower aggression.
Parenting and childhood aggression have long been linked. Parents who inconsistently enforce rules tend to have children with more aggressive behavior, while greater positive parenting, such as praising and positively engaging with children, is associated with less aggression. These findings can easily be interpreted as evidence that parenting produces differences in children’s behavior.
But families are more complicated. Children can affect their parents just as parents can affect their children. Biological parents and children also share genes, meaning some of the genetic factors associated with a parent’s behavior could be inherited by their children and influence the children’s behavior.
Led by Joanna K. Bright of King’s College London, the researchers addressed these problems using two genetically informative studies of children between about 4.5 and 8 years of age. Both studies used the same questionnaires to measure inconsistent discipline, positive parenting and child aggression, allowing the researchers to check whether the results held across different samples and methods.
The first drew on Norway’s Mother, Father and Child Cohort Study, using extended-family data involving 53,532 children born to 42,538 mothers, who reported on their parenting and their children’s behavior when the children were 5 years old. By comparing families with different degrees of genetic relatedness, including twins and their children, the researchers could estimate how much of the relationship between parenting and aggression was associated with shared genetics.
The second dataset came from the U.S. Early Growth and Development Study and contained 561 adoption triads, each made up of an adopted child, the adoptive parents and the birth parents. The children, 57% of whom were male, were adopted shortly after birth and assessed at ages 4.5, 6, 7 and 8. Because adoptive parents and children did not share genes, associations between their behaviors provided a way of examining environmental pathways without the complication of genes inherited from those parents.
The results suggested a more complicated relationship than parenting simply causing aggression. In the Norwegian study, the correlation between inconsistent discipline and child aggression was modest. About 47% of this association was attributed to shared genetic factors, while 53% remained after accounting for genetic transmission.
When the researchers investigated that remaining relationship, the evidence pointed from child to parent. The best-fitting model included a path from child aggression to inconsistent maternal discipline but no path from discipline to aggression. The adoption study showed a similar pattern: children’s aggression was linked to more inconsistent discipline at the same age and predicted more inconsistent discipline at later ages, while paths from mothers’ discipline to children’s aggression were not statistically significant.
Bright and colleagues concluded that “childhood aggression drives inconsistent parenting beyond shared genetic influences.”
Sensitivity analyses using fathers’ reports in the adoption study painted a somewhat different picture. When fathers reported on both their own parenting and their children’s behavior, inconsistent discipline and child aggression appeared to influence each other in both directions at the same time point, though not over longer periods. When one parent’s report of child aggression was paired with the other parent’s report of parenting, no significant links emerged, which the authors note could mean that relying on the same person to report both behaviors inflates associations.
Positive parenting produced another important finding. Although greater positive parenting was associated with lower aggression in the Norwegian sample, the researchers estimated that the association was completely explained by shared genetic influences. In the adoption sample, the models found no evidence that positive parenting and aggression influenced each other in either direction.
The results did not differ meaningfully between boys and girls. The authors suggest that clinicians should recognize that childhood aggression can contribute to inconsistent discipline, and that interventions focused only on encouraging consistent discipline may be insufficient.
Some limitations should be noted. The authors caution that their questionnaires captured relatively narrow aspects of parenting and aggression, relied primarily on mothers’ reports, and were drawn from relatively socioeconomically advantaged families. The two samples also used somewhat different versions of the aggression measure, which captured defiant behavior as well as physical aggression.
The Norwegian analysis was based on a single time point and could not account for the possibility that parents choose partners with similar traits. The data were also collected between roughly 10 and 23 years ago, and parenting norms may have shifted since then.
The study, “Triangulating evidence for genetic and environmental components of associations between parental behaviours and aggressive behaviour in children,” was authored by Joanna K. Bright, Yasmin I. Ahmadzadeh, Olakunle Oginni, Essi Viding, Leslie D. Leve, Jenae M. Neiderhiser, Daniel S. Shaw, Misaki N. Natsuaki, Jody M. Ganiban, Eivind Ystrom and Tom A. McAdams.