It is well known that child maltreatment can affect people's behaviors in profound ways, leading to greater rates of psychiatric disorders, substance abuse and relationship difficulties. But less well known is that poor early care may also affect the very functioning of our genes, in essence, by sparking a chemical reaction in the brain that influences how stress-related genes express themselves, says Michael Meaney, PhD, who directs the Sackler Program for Epigenetics and Psychobiology at McGill University.
At this year's Neal Miller Distinguished Lecture at APA's Annual Convention, Meaney will discuss the 35 years of research with rats—and more recently with humans—that led him to this finding.
In his initial work, Meaney demonstrated that adult offspring of rats that had been licked frequently as pups showed less anxiety and hormonal changes in response to stress than those that were licked less.
From there, Meaney embarked on a series of studies examining how this finding plays out on the molecular level. Over time, he observed a complex chain of events whereby the mother's licking behavior activates chemical signals in the hippocampus, which in turn influences the number of molecules that attach themselves to the genes that regulate the stress response. The more of these molecules cling to gene, the more suppressed the gene's functioning, he has found.
More recently he's been able to corroborate these findings in humans, by examining the brains of deceased people shown to have had neglectful or abusive childhoods. He is also conducting studies with monkeys to further cement the link in humans.
The findings aren't another justification for "blaming the mother," Meaney emphasizes. Indeed, other research shows that rats become high- or low-licking mothers depending on how nurturing or stressful their own environments were.
"There's a context in which this mother-infant interaction occurs," he says. "It's the quality of the context that really counts."
Meaney will discuss these findings at his session at 4 p.m., Aug. 8.