TORONTO - Childhood trauma can alter the way genes in the brain work, potentially putting an individual at increased risk for suicide later in life, Canadian researchers have discovered.
A team of scientists from McGill University analyzed brain tissue from 12 suicide victims who had been abused as children and compared them to the tissue of 12 suicide victims who had not been traumatized and 12 people who died from other causes.
They found that the brain tissue from the abused group showed "epigenetic" changes that affect a person's response to stress, which is known to increase the risk of suicide.
Genes are inherited from a person's parents and remain unchanged throughout life. But exposure to environmental influences, be it social trauma or chemical substances, can alter how those genes function.
These changes, in which the DNA is marked by proteins, are known as epigenetic alterations and can occur even during gestation.
In the brain cells of suicide victims who had suffered severe sexual or physical abuse or neglect, the Montreal researchers found epigenetic markings in a gene that affects how a person reacts to stress.
"And what we found was that those individuals that had been abused and neglected during childhood were more likely to have increased epigenetic regulation of this gene," co-author Dr. Gustavo Turecki, a psychiatrist and neuroscientist, said from Montreal.
"What that means is that these people would be less well-prepared to deal with stress and to react to stress."
The samples of tissue used in the study came from the Quebec Suicide Brain Bank, which houses the brains - donated by families for the purposes of research - of about 200 people who died from suicide or other causes.
The McGill scientists, whose paper is published in this week's issue of the journal Nature Neuroscience, say that identifying epigenetic changes in abuse victims could one day pave the way for drugs that would reverse the damage.
To do that, said co-author Moshe Szyf, researchers would have to find similar epigenetic makings in the DNA of a person's blood, since brain tissue can only be analyzed after death.
"The implications at this stage are you want to identify these people and then probably offer them some sort of intervention," said Szyf, an epigeneticist in McGill's department of pharmacology and therapeutics. The goal, he said, would be to find drugs that could reverse the epigenetic changes.
"We don't know how to do it yet. We might know in the future, but we don't know how to do it now."
Dr. John Strauss, a child psychiatrist at the Centre for Addiction and Mental Health in Toronto, said the McGill study is important because it brings to "psychiatric disorders a way of explaining potential gene-environment interactions."
The difficulty is translating the method into subjects that are living, he said.
"Obviously, if there were some kind of marker that you could check in individuals to see if they are more at risk (for suicide), it might aid identification. It might also be used as a potential marker to follow people."
Strauss said such a test would allow doctors to see if epigenetic changes that occurred as a result of early trauma had "switched back," at which point drugs or other therapy could be reduced in frequency or intensity.
"But you need really accessible samples."
Szyf said the optimistic message from the study is that changes in the function of genes transformed by environmental factors are potentially reversible.
"I think what's nice about the study is we can see marks of early life in the genes of older people," he said. "And that illustrates the power of epigenetics because it serves as a memory of environmental exposure."
For instance, it's known that toxic chemicals like lead, mercury and PCBs can alter the function of a person's genes and result in disease, including some cancers.
"But it seems that social exposures are as toxic and can cause exactly the same kind of changes," Szyf said. "And we should be aware of the impact a bad social environment can have on our health."
