Survivors of child abuse may be more likely to kill themselves as adults because their early experiences change the way a critical gene works in the brain, according to new research that could shed light on the biology of suicide.

A study that compared male suicide victims with men who died in accidents found differences in chemical markers that determine how brain genes are switched on and off.

As all 13 suicide cases, but none of the accident victims, had been abused as children, the findings suggest that these “epigenetic” changes in gene activity may have been created by difficult environments early in life.

The suggestion is that such extreme stress may permanently change the way important brain genes function, leaving people vulnerable to future mental illness and suicide.

The results, from a team led by Professor Moshe Szyf of McGill University in Montreal, could lead doctors to test for these epigenetic markings to identify people at risk. It may even be possible to develop drugs that erase them, though both prospects are probably at least a decade away. Professor Szyf said: “It's possible the changes in epigenetic markers were caused by the exposure to childhood abuse, although in humans it's difficult to establish causality between childhood and epigenetic markers in the way we have established this in animal subjects.

“The big remaining questions are whether scientists could detect similar changes in blood DNA — which could lead to diagnostic tests — and whether we could design interventions to erase these differences.”

The results, which are published in the journal Public Library of Science One, also illustrate science's growing understanding of the importance of epigenetics to human health and behaviour.

While the genes we inherit from our parents remain unchanged throughout life, with the exception of random mutations of the sort that cause cancer, the way in which they operate in cells can be heavily influenced by the environment.

Epigenetics, which means “on top of genetics” in Greek, is the phenomenon by which the genome can remember these environmental effects. Professor Szyf has previously shown with rats that different patterns of maternal care can influence the expression of genes involved in fear and stress in their young.

In the new study, the scientists suggested that epigenetic differences in the gene which produces ribosomal RNA (rRNA), a chemical that helps make proteins, could have influenced the brain development of the suicide victims and impaired their mental health. “It is tempting to speculate that epigenetic processes mediate effects of social adversity that persist into adulthood and are known to enhance suicide risk,” researchers said.

Risk factors

— Suicidal behavior tends to run in families: an indication that shared genes, shared environment, or both, are involved

— In 2006 there were 5,554 suicides among people aged 15 and over in Britain — almost 1 per cent of total deaths in that age group. Three quarters were men

— Identical twins are more likely to commit suicide or to attempt suicide than are non-identical twins

— Non-genetic risk factors within families include a history of abuse or neglect. Childhood abuse is associated with an increased risk of psychopathology and altered neural development

— Studies of rodents have suggested that the quality of maternal care can change the activity of genes that are associated with stress and fear in humans

— A study called Suicide in Avon found that 80 per cent of young men who had died by suicide had no contact with their GP, psychiatrist or other support agency in the four weeks before their deaths

—Young people who commit suicide are more likely than their peers to have had a friend or relative who has died by suicide

Sources: plosone.org; statistics.gov.uk; mind.org

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