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A new study published in the Journal of Child Development looked at whether the age of parents at the time of their children’s birth could result in behavior problems. Couples who have children at later ages are often counselled about risks of increased maternal age (e.g. Down syndrome) but increasingly a risk has been documented for increased paternal age and autism and schizophrenia.

“Our initial expectation was that child behavior problems would increase as parental age increased,” lead study author Mariëlle Zondervan-Zwijnenburg told us. “We had this expectation, because a similar relation between paternal age and autism and schizophrenia is well documented. We also know that there are several mechanisms that make parenthood at an advanced age disadvantageous from a biological perspective. On the other hand, we knew that there were also studies that reported mixed findings.”

The main question Zondervan-Zwijnenburg and colleagues Sabine Veldkamp and Dorret Boomsma had was to which extent they would see similar results for common childhood behavioral problems when using advanced methods and an explicit replication step built into the design.

“We were wondering whether the relation that has been described of parental age with psychiatric disorders also held for more common mental health problems,” Zondervan-Zwijnenburg told us. “We also knew that we had the data from multiple large cohort studies in the Netherlands to investigate this relation and that we could combine the information with cutting-edge Bayesian methods.”

The researchers used data from four cohorts on internalizing and externalizing behavior problems as reported by the children themselves, their parents and their teachers. They reserved half of the data within each cohort for exploration and the other half for confirmation.  

“In the exploratory phase, we ran analyses to derive a set of competing informative hypotheses about the relation between parental age and child behavioral problems,” Zondervan-Zwijnenburg told us. “In the  confirmatory phase, we used Bayes factors to calculate the relative support for each of these informative hypotheses in each cohort.”

Next, the researchers computed the relative support for the hypotheses by all cohorts. The hypotheses that received the most support from all cohorts (irrespective of measurement instruments and cohort-specificities), was the most likely robust hypothesis.  

“We found that parental age was unrelated to internalizing behavior problems that consist of anxiety, depressive symptoms and withdrawn behaviors,” Zondervan-Zwijnenburg told us. “For externalizing problems (e.g., physical aggression, disobeying rules) we found that increasing parental age led to more positive child outcomes (i.e., fewer problems reported). We know that higher socio-economic status in parents goes together with later parenthood and better child outcomes, so we included that factor in our analyses as well. Socio-economic status indeed explained part of our results, but not everything. Thus, we found a beneficial relation between increasing parental age and child externalizing problem behaviors, and this relation was not fully due to socio-economic status.”

Initially, the researchers were surprised with their findings, as their main expectation was that increasing age would lead to detrimental results. Apparently, the biological disadvantages of increasing age are compensated, or even more than compensated, by contextual factors. Socio-economic status is one of these contextual factors.  

Furthermore, they learned from other research that older parents on average have a more sensitive parenting style with more structure. Another important factor can be that parents who have more externalizing problems themselves, are probably more impulsive, which can also cause them to have children at a younger age to whom they transfer their own problematic behaviors. 

“Our results imply that older parents do not have to worry that their age negatively affects their children with respect to common childhood problem behaviors,” Zondervan-Zwijnenburg told us. “This conclusion holds for both internalizing and externalizing problems. We are currently also investigating Attention Deficit Hyperactivity Disorder, educational attainment and IQ.”