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Stress, abuse damages childhood genes

A handout photograph shows "Elizabeth", who says she was raped by 10 peacekeepers in the Ivory Coast

The study may explain why childhood abuse can lead to depression, other mental health effects and suicide (Source: Ho New/Reuters)


Canadian researchers found early childhood abuse can change the expression of a gene which is important for responding to stress.

The study, by Professor Michael Meaney and colleagues at McGill University, is published online today in Nature Neuroscience.

The researchers studied the brains of 24 suicide victims - 12 who had suffered severe childhood abuse, which included physical abuse, neglect or sexual contact, and 12 who had not been abused.

They also studied the brains of 12 accident victims who had not been abused.

Those who had been abused had lower levels of expression of the gene for the glucocorticoid receptor, which is critical for the stress response pathway.

Rat studies have previously shown that early childhood experiences can cause long-term genetic changes in the pathway, but this is the first evidence in humans.

"Childhood adversity might alter the development of systems that regulate stress responses ... enhancing the effect of stress in adulthood and vulnerability for mood disorders," the researchers say.

Flood of hormones

University of Newcastle professor of perinatal and infant psychiatry, Louise Newman, says if children are abused early, they are flooded with stress-related hormones such as cortisol and adrenaline.

"This impacts directly on how the brain develops and the stress regulation mechanism. It becomes highly stressed so it's like setting the thermostat on high, setting up a system which regulates stress less efficiently," she says.

"Also it impacts on the area which controls feelings, so they're more likely to be highly stressed, have difficulties with anger and emotions, and be prone to self-harm, anxiety, suicide and depression."

Clinical psychologist and director of Queensland University of Technology's Institute of Health and Biomedical Innovation, Professor Ross Young says being raised in a stable, safe environment helps us deal with stress in adulthood.

He says severe childhood abuse, consistent and repeated abuse or being raised in a traumatic environment, is a risk factor for stress-related psychological problems.

"Child abuse can change the structure of the brain," says Young.

Path to suicide

"[The study] found significant differences in stress related hormone receptors in abused suicide victims compared with others, and evidence that parts of the gene may be switched off by abuse, leading to abnormal stress responses in adulthood.

"In essence, childhood abuse appears to interact with a stress hormone related gene as one potential path to suicide."

Director of the Genetics of Learning Disability Service at Hunter Genetics, Dr Anna Hackett says it shows those subjected to abuse have an increased risk of suicide due to changes in the stress pathway.

"It appears that an epigenetic process (methylation) occurs to a greater extent in a glucocorticoid receptor promoter gene in suicide victims subject to childhood abuse than other groups," she says.

"Increased methylation occurs early in a child's development when exposed to abuse and has a long term effect on an individual's response to stress."

The experts agree it reinforces the importance of interventions to prevent abuse.

Tags: child-abuse, suicide, child-health-and-behaviour, genetics