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Canadian researchers may have discovered the underlying cause that leads some people to commit suicide or suffer major depression, a finding that could revolutionize how mental disorders are treated.

After examining the brains of people who committed suicide, a team of scientists discovered an abundance of protein affecting a particular gene that controls anxiety and stress compared with the brains of people who had died of heart attacks or other natural causes.

The study is part of the burgeoning field of epigenetics that examines how genes are regulated, or turned on and off.

"It's a really new avenue of research," said Michael Poulter, lead researcher and professor in the physiology and pharmacology department at the University of Western Ontario.

"There's only a few people around the world that are doing it."

In this study, researchers found that people who committed suicide had elevated levels of a specific protein.

They believe the abundance of the protein alters or modifies a gene that normally helps people cope with stress. As a result of the change, the gene shuts down and malfunctions, inhibiting the individual's ability to handle stress and cope with anxiety.

The researchers, whose findings were published in this month's Biological Psychiatry journal, aren't sure why some people have higher levels of the protein. But Dr. Poulter believes it is somehow linked to stressful life events and how people may cope with them in different ways.

The discovery marks the first time researchers have shown an abundance of protein may be associated with depression and suicidal behaviour and may lead to major breakthroughs in treatment of such disorders.

That's because many of the current treatments for depressive disorders focus on addressing chemical imbalances in the brain. But those imbalances may just be manifestations or symptoms of the depression, which could actually be caused by the genetic malfunctions identified in this study, Dr. Poulter said.

One of the key areas of focus in creating future treatment for mental illness may be developing a drug that could inhibit the overactivity of the protein that is causing the gene to malfunction, Dr. Poulter said.

"If we can give a drug that provides this long-term relief, I think we're on to something much more effective and perhaps at the root of the illness," said Dr. Poulter, who is also a scientist at the Robarts Research Institute in London, Ont. "There might be a whole new class of antidepressant drugs out there within a few years."

One of the major questions this research raises is whether the abundance of protein and subsequent gene malfunction noted in the study is exclusive to people who committed suicide. Dr. Poulter said it would be worthwhile to determine whether people who suffer from major depression, but die from other causes, have the same genetic malfunctions as those who take their own lives. However, that question will be extremely difficult to answer because so few people are willing to donate their brains for scientific purposes.

"[It's a] tough cohort to get. We've collected four brains like that in three years," he said.

While the research in the field of genetic regulation is still in its relative infancy, it holds significant promise for helping scientists to understand how certain genes function and what may lead to depression and other disorders.

"We've identified a fundamental process that controls the patterning of gene expression," Dr. Poulter said. "We've shown that it is disturbed in a neurological disorder."

Dr. Poulter said it is still too early to say whether prolonged periods of stress and anxiety throughout a person's life may have a greater impact on the genes that control how well people cope with stress and anxiety.

"We all cope differently," he said. "Some people like stress. It's really tough."