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As reported by Benedict Carey in the NY Times, a study in Nature Neuroscience underpins the impact of stress on early brain development.
Over the past decade researchers at McGill University in Montreal, led by Michael Meaney, have shown that affectionate mothering alters the expression of genes in animals. It allows animals to dampen their physiological response to stress.
The biological buffers are then passed on to the next generations: rodents and nonhuman primates biologically primed to handle stress tend to be more nurturing to their own offspring.
For the first time, researchers have direct evidence that the same system is at work in humans.
Psychiatrists have known for years that children who are abused or neglected run a high risk of developing mental problems later in life. Problems may range from anxiety and depression to substance abuse, and most seriously, suicide.
McGill University researchers analyzed brain tissue from adults who had committed suicide, and found key genetic changes in those who had suffered abuse as a child.
The abuse affects the production of a receptor known to be involved in stress responses.
Previous research has shown that abuse in childhood is associated with an increased reaction to stressful circumstances. But exactly how environmental factors interact with genes and contribute to depression or other mental disorders in adulthood is not well understood.
The research team examined the gene for the glucocorticoid receptor — which helps control the response to stress — in a specific brain region. Twelve of the suicide victims had a history of child abuse and 12 had not suffered abuse when younger.
They found chemical changes which reduced the activity of the gene in those who suffered child abuse. And they showed this reduced activity leads to fewer gludocorticoid receptors.
Those affected would have had an abnormally heightened response to stress, the researchers said.
According to Jaak Panskepp, adjunct professor at Washington State University, who was not involved in this research, the study “extends the animal work on the regulation of stress to humans in a dramatic way.”
He adds that the study suggests pathways that have promoted the psychic pain that makes life intolerable.
Because of individual differences in the genetic machinery that regulates stress response, experts say, many people manage their distress despite awful childhoods. Others find solace in other people, which can help them regulate the inevital difficulties of life.
Says Dr Steven Hyman, professor of neurobiology at Harvard, “The bottom line is that this is a terrific line of work, but there is a very long way to go either to understand the effects of early experience or the causes of mental disorders.
Says Michel Meaney, “If you’re a public health individual or a child psychologist you could say this shows you nothing you didn’t alsready know,” he says.
“But until you show the biological process, many people in government and policy-makers are reluctant to believe it’s real.”
It may be true that a drug could reverse these effects; this research could have an impact on drug development.
Dr Jonathan Mill, of the Institute of Psychiatry at Kings College London says the research adds to growing evidence that environmental factors can alter the expression of genes — a process known as epigenetics.
“Whilst these results obviously need to be replicated, they provide a mechanism by which experiences early in life can have an effect on behavior later in adulthood.”
Dr Mills adds, “The exciting thing about epigenetic alterations is that they are potentially reversible, and thus perhaps a future target for therapeutic intervention.”
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