Researchers say that chronic aggressive behavior found in some boys may be a result of epigenetic changes during pregnancy and early childhood, according to two studies published in the journal PLOS ONE.
Both studies were led by Richard E. Tremblay of the University of Montreal and Moshe Szyf of McGill University.
For the first study, the team analyzed the blood samples of 32 male individuals from Quebec with a disadvantaged background, who had suffered from chronic physical aggression since childhood.
The males were selected from two longitudinal studies, conducted by Prof. Tremblay’s team, that spanned almost a 30-year follow-up period, following the participants from childhood to adulthood.
Alongside this group, the team also examined the blood samples of a group of males from the same background, but who did not suffer from chronic aggression.
The results from this study revealed that blood levels of four biomarkers of inflammation, called cykotines, were lower in men who showed average levels of aggressive behavior between 6 and 15 years of age.
The researchers say this enabled them to distinguish men who had a history of chronic physical aggression from those who did not.
In the second study, the research team set out to see whether there were any differences in DNA methylation patterns in the same chronic aggressive participants.
They explain that methylation is an “epigenetic modification” of DNA linked to parental imprinting, which plays a role in regulating gene expression.
The results from this study revealed a link between DNA methylation in cykotines and their regulators in T cells and monocytes and male physical aggression.
According to Prof. Szyf, the prenatal and postnatal environment could cause the differences in biomarkers linked to chronic aggression.
The researchers point out that many animal studies have shown that hostile environments during pregnancy and early childhood may have an impact on gene methylation and gene programming, which may lead to problems with brain development and the ability to control aggressive behavior.
Furthermore, they note that previous research from the team has suggested that men with aggressive pasts all have the same thing in common – their mother’s characteristics.
“They are usually young mothers at the birth of their first child, with low education, often suffering from mental health problems, and with substance use problems,” says Prof. Tremblay.
He notes that because these mothers experience significant difficulties during pregnancy and their child’s early days, this could potentially have an impact on gene expression linked to brain development, the immune system and other biological systems critical to child’s development.
Prof. Tremblay says that as chronic aggressive behavior is much more common in boys from disadvantaged families, this means that potential participants for future studies are difficult to find.
He notes, however, that the team is looking to analyze the impact of the socioeconomic environment on the third generation, now that the participants of this study are adults and have children themselves.
Although he says there are no studies that have looked at this before, he says he expects to see “significant intergenerational ties,” considering a link has been made between “parental criminality of the first generation and the behavior of their children.”
He adds: “If our results show that behavioral problems originate from as far back as pregnancy, it means that we can reduce violence through preventive intervention from as early as pregnancy.”