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Aggression and Epigenetics

When the psychologist Richard Tremblay began studying children with severe behavioral problems in Montreal in the 1980s he had no idea that his pursuits would lead him down a path toward epigenetics.

But his efforts to understand the links between aggressive behavior and how young children are treated, and how early interventions and a nurturing environment can help these children, eventually spurred him to seek out a biological basis for these behavior patterns, Nature's Stephen Hall writes in a profile of Tremblay.

Tremblay, now at University College Dublin, has teamed with scientists at McGill University and the NIH to run a longitudinal study of how nurturing or adverse environments can impact gene expression, and affect people across the lifespan.

Hall writes that Tremblay's journey toward investigating epigenetic signatures that may be linked to aggressiveness and other behavioral problems was not a straight path, and how at several steps along the way he was influenced by other researchers and by his experiences with children, and with dangerous criminals in prison.

For example, he was influenced by a primate study that found distinct differences in DNA-methylation patterns between monkeys that were nurtured and those that were separated from their mothers – or "the epigenetic residue of post-natal adversity," Hall writes. This impact affected more than 4,000 genes, including one that is involved in the function of serotonin, which in low levels has been associated with elevated stress and aggression in humans.

Last July, Tremblay and his partner reported that men with a history of chronic aggression dating into childhood had significantly lower blood levels of immune molecules called cytokines. The partners also have shown that men in one study who have a long history of aggression also had a distinctly different pattern of DNA methylation in the genes that encode cytokines than men who have a less aggressive behavioral profile.

Tremblay says "it seems relatively clear that there are large differences in DNA methylation between those who have a history of chronic aggression compared to those who have normal development."

James Heckman, a Nobel-winning economist at the University of Chicago, tells Hall that there is a body of evidence which shows that early life experiences affect long-term outcomes such as crime, health, and income.

Heckman is now working with Tremblay on a study to find out if early interventions like prenatal and early childhood support measures can help disadvantaged mothers to raise healthier and happier children.