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In two new studies conducted by a team from the University of Montreal and McGill University, the researchers examined the possible sources of chronic aggressive behavior seen in some young boys. These studies focused on children from disadvantaged families. The researchers believe that due to epigenetic changes, which are changes in gene expression, during pregnancy and early childhoods, these young boys might be more prone to aggression than other boys.

In the first study, headed by Richard E. Tremblay, professor emeritus at the University of Montreal, the researchers measured the levels of four biomarkers of inflammation in men. The men who were more aggressive during the ages of six to 15 had lower blood levels of these biomarkers than men who had average levels of aggression. The four biomarkers are called cytokines. In the second study, the researchers examined a group of aggressive males. They reported that the more aggressive men's DNA encoding process of the cytokines revealed different methylation patterns than the group of men with average aggression.

"Methylation is an epigenetic modification - hence reversible - of DNA, in relation to parental imprinting. It plays a role in regulating gene expression," commented fellow researcher Moshe Szyf reported by Medical Xpress.

Aside from discovering epigenetic changes, the researchers also noted that the mothers of the chronically aggressive young males had similarities. The researchers observed that these mothers tended to be young and less educated. They were also more likely to have substance abuse issues and mental health problems. The researchers believe that these difficulties that the mothers went through could have contributed to the epigenetic changes.

The two studies focused on 32 men over the course of almost 30 years. The first study had involved young males from Quebec who were from disadvantaged backgrounds. The second study focused on a representative sample of children in kindergarten in Quebec from 1986 to 1987.

"We are studying the impact of the socioeconomic environment on the third generation, now that these children are grown up and have children," Tremblay noted. He expects to find "significant intergenerational ties, since [they] observed an association between parental criminality of the first generation and the behavior of their children."

The studies were published in PLOS ONE.