OTTAWA -- Canadian doctors said Friday they had discovered a genetic mutation that increased the chance of suicide and predicted that a test to identify those at high risk of killing themselves could be available by 2002.
The results of a 10-year study by a team at the Royal Ottawa Hospital into why depressed people kill themselves are a clear sign that suicide is a largely genetic phenomenon and not related, as often thought, to weakness of character.There are enormous implications to the findings. Creation of a successful test may lead to more careful treatment of depressed patients who carry the mutation but may raise fears that those with the marker could be discriminated against.
The team found that depressed people with a mutation in the gene encoding for a serotonin 2A receptor -- a message-carrying chemical linked to mood -- were more than twice as likely to commit suicide than those without the mutation.
However, team member Dr. Pavel Hrdina cautioned that the study's results would have to be duplicated before they could be deemed scientifically valid.
"The major finding of the study was that suicidal tendencies were much more frequent in depressed individuals carrying the (mutation)," he told Reuters.
Hrdina said a "suicide test" could be devised within two years to help identify those depressed people at higher risk of killing themselves.
"This is a warning sign, an early marker. There might be depressed people who don't have suicidal tendencies, who wouldn't know at the time (they had the mutation). Those patients would be more closely watched than others," he said.
According to the World Health Organization, suicide was the 12th leading cause of death in 1998, when 948,000 people died of self-inflicted injuries. Experts predict that cases of suicide and depression will soar over the next 20 years.
Hrdina said that depressed people with suicidal tendencies almost certainly carried other genetic mutations which combined to trigger suicidal inclinations.
The serotonin 2A receptor mutation was therefore a reliable sign that someone might kill themselves rather than being the only cause for suicide.
The results have enormous moral implications -- what would happen if companies forced their employees to take the test and then discriminated against those found to carry the mutation?
Would sufferers be denied life insurance or barred from flying planes or driving school buses?
"That is a question which society will have to decide. The positive side of this is that if there is a biological or genetic test one can give hope that with treatment this can be handled," said Hrdina.
"If this is just let go and we don't encourage people to (learn) about it -- and they are not seeking medical help to treat their symptoms of depression or suicidality -- they may eventually end up losing their lives."
Dr. David Bakish, a suicide specialist on the team, said tests showed that there was no reduction in the level of mutant serotonin receptor genes in patients who had been successfully treated for depression.
"This is very meaningful. It suggests that some people may be biologically predisposed to suicidal thoughts, and that suicide, so often stigmatized, is hardly a character flaw," he said.
The Ottawa researchers started by studying the brains of people who had killed themselves in Hungary, a country with one of the world's highest suicide rates. The tests showed large amounts of the mutated gene.
The team then carried out a long-term study on a group of 120 depressed people in Canada.
"We divided the depressed patients into suicidal and non-suicidal and we found the frequency of the gene variety was significantly higher in the suicidal patients," Hrdina said.
"We concluded that the carriers of this particular combination in the gene were at double the risk for suicidal tendencies."
Hrdina said the Royal Ottawa Hospital team was now looking at whether people suffering from other mental disorders such as schizophrenia also carry the mutation.
"There is a stigma about these things, people shy away. But it will help them when they realize (being suicidal) is not a crazy state, or something that comes out of the air and cannot be handled, but has a biological link," Hrdina said.
The team's findings will be published in the February 7 issue of the American Journal of Medical Genetics.