Chronic aggressive behavior in boys: Epigenetic sources?

Chronic aggressive behaviour exhibited by some boys from disadvantaged families may be due to epigenetic changes during pregnancy and early childhood. This is highlighted by two studies conducted by a team led by Richard E. Tremblay, professor emeritus at the University of Montreal and Moshe Szyf, professor at McGill University, published in the journal PLOS ONE. The first author of the two papers, Nadine Provençal, was jointly supervised by professors Szyf and Tremblay.

Epigenetic changes possibly related to the prenatal environment

In the first study, published in July, the team found that among men who had chronic aggressive behaviour during childhood and adolescence, blood levels of four of inflammation were lower than in men who exhibited average levels of aggressive behaviour in their youth, from 6 to 15 years of age. "This means that using four specific biomarkers of inflammation, called cytokines, we were able to distinguish men with chronic histories from those without," says Tremblay, a researcher specializing in . In the second study, it was observed in the same men with aggressive pasts, that the DNA encoding the cytokines showed methylation patterns different from those of the comparison group.

"Methylation is an epigenetic modification—hence reversible—of DNA, in relation to parental imprinting. It plays a role in regulating ", says Szyf, who specializes in epigenetics.

The pre- and postnatal environment could cause these differences in biomarkers associated with chronic aggression," Szyf added. Various studies conducted with animals show that hostile environments during pregnancy and have an impact on gene methylation and gene programming leading to problems with , particularly in regard to the control of aggressive behaviour.

Previous work by Tremblay's team suggest that men with aggressive pasts have one thing in common: the characteristics of their mothers. "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," Tremblay explained. The significant difficulties these mothers experienced during pregnancy and the early childhood of their child may have an impact on the expression of genes related to brain development, the immune system, and many other biological systems critical for the development of their child.

A nearly 30-year follow-up

The blood samples used in the studies published this summer in PLOS ONE were collected from 32 participants who took part in either of two longitudinal studies that begun nearly 30 years ago by Tremblay's team. The first study followed young Quebecers from disadvantaged backgrounds, while the second involved a representative sample of children who were in kindergarten in Quebec in 1986-87.

It is important to note that in disadvantaged families, the rate of boys with chronic represents about 4% of the population. This greatly restricts the selection of potential participants. "Once they are adults, they are difficult to find because they have disorganized lifestyles," Tremblay said.

A prevention perspective

This difficulty has not stopped him from pursuing his research further. "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. No study has yet been published on the subject, he anticipates "significant intergenerational ties, since we observed an association between parental criminality of the first generation and the behaviour of their children."

Nevertheless, the researcher, who has conducted his work for decades with a prevention perspective, is optimistic. "If our results show that behavioural problems originate from as far back as pregnancy, it means that we can reduce violence through preventive intervention from as early as pregnancy," says Tremblay. We have already shown that support given to families of aggressive boys in kindergarten prevents school dropout and crime in adulthood.

More information: Childhood chronic physical aggression associates with adult cytokine levels in plasma. PLoS One. 2013 Jul 26;8(7):e69481. doi: 10.1371/journal.pone.0069481. Print 2013.

add to favorites email to friend print save as pdf

Related Stories

Parents' genes may influence children's back-to-school fears

Sep 10, 2013

Many parents may have noticed their children seemed on edge during their first week of school. They may have been agitated, withdrawn or more focused on themselves, rather than what was going on around them. Such behaviours ...

DNA changes during pregnancy persist into childhood

Sep 04, 2013

Even before they are born, babies accumulate changes in their DNA through a process called DNA methylation that may interfere with gene expression, and in turn, their health as they grow up. But until now it's been unclear ...

Research grasps in-utero testosterone and behaviour ties

Aug 13, 2013

While childhood behavioural difficulties do not appear to be linked to increased testosterone exposure in the womb, a relationship between antenatal testosterone and attention span in boys and withdrawn behaviour ...

Recommended for you

Some people may be pre-wired to be bilingual

6 hours ago

(HealthDay)—Some people's brains seem pre-wired to acquire a second language, new research suggests. But anyone who tries to move beyond their mother tongue will likely gain a brain boost, the small study ...

Elderly brains learn, but maybe too much

15 hours ago

A new study led by Brown University reports that older learners retained the mental flexibility needed to learn a visual perception task but were not as good as younger people at filtering out irrelevant ...

Inpatient psychotherapy is effective in Germany

17 hours ago

Sarah Liebherz (Department of Medical Psychology, University Medical Centre Hamburg-Eppendorf) and Sven Rabung (Institute of Psychology, Alpen-Adria-Universität Klagenfurt) have examined 59 studies conducted between 1977 ...

A game changer to boost literacy and maths skills

19 hours ago

(Medical Xpress)—Finding the best way to teach reading has been an ongoing challenge for decades, especially for those children in underprivileged areas who fail to learn to read. What is the magic ingredient that will ...

User comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.