Genetically-informed study shows early motherhood is linked to offspring offending, but does not cause it

A new study suggests that previous research has overestimated the impact of young motherhood on offspring criminal and antisocial behavior. The study, published in Psychiatry Researchfound that the relationship between maternal age at birth and offspring adolescent offending disappeared after accounting for demographic and family variables.

“My research focuses on intergenerational influences on criminal behavior, as parents are believed to have an important influence on the behavior of their children, including antisocial or criminal behavior,” said study author Steve van de Weijer, a senior researcher at the Netherlands Institute for the Study of Crime and Law Enforcement.

“Previous studies have consistently found that young motherhood is a risk factor for problematic behavior in their offspring. However, it was less clear to what extent this reflects a causal effect or whether this link is the consequence of other factors that lead to both early motherhood and offspring offending.”

For his study, Van de Weijer analyzed register data from Statistics Netherlands, a government agency responsible for providing data on all Dutch citizens from several official sources. In addition to police data, the agency collects various demographic and socioeconomic information, such as household income, education levels, employment status, and maternal and paternal death.

The sample included 2,098,815 individuals who were born in the Netherlands between 1991 and 2001. Approximately 11% of the sample offended during adolescence.

Van de Weijer found that those with a younger mother were more likely to have been the suspect of at least one crime between the ages of 12 and 18. But the relationship between maternal age at birth and offspring adolescent offending was no longer statistically significant after accounting for control variables.

“Children in the Netherlands are more likely to be involved in criminal behavior during adolescence if they have a younger mother: a one year increase in the age of the mother at birth is associated with a 6.4 percent decrease in the odds of offspring offending,” van de Weijer told PsyPost.

“This association, however, disappears after taking into account various demographic and socio-economic characteristics and after controlling for unmeasured family factors, such as genetic factors, by making a comparison between cousins ​​with mothers of different ages. This shows that the relationship between early motherhood and offspring adolescent offending in this study is a spurious relationship and does not reflect a causal effect.”

As with any study, however, the new research includes some caveats.

“This study was based on official register data, such as police data to measure adolescent offending,” van de Weijer explained. “As a majority of criminal acts are never detected by the police, it is very likely that various sample members were considered as non-offenders while they might in fact have committed crimes for which they were simply never arrested.”

“Moreover, this study is based on data from The Netherlands, where rates of teenage motherhood are relatively low and where there is an extensive social welfare system. Therefore, results might not be generalizable to countries in which young mothers are more often teenagers and where there is no extensive social welfare system that might mitigate the negative consequences of young motherhood.”

Nevertheless, the findings highlight the importance of genetically-informed research designs.

“The results of this study are in line with a growing amount of research that shows that associations between parental and offspring behaviors are attenuated when comparisons are made within families rather than between unrelated persons,” van de Weijer told PsyPost. “This illustrates that unmeasured family factors – genetic factors and/or shared environments – (partially) explain intergenerational links. It is therefore important that studies use family-based research designs when investigating intergenerational effects, in order to take into account such unmeasured family factors.”

The study, “No causal relationship between early motherhood and offspring adolescent offending: Empirical evidence from a genetically-informed study”, was authored by Steve van de Weijer.