Research Update
Suicide linked to serotonin gene
CMAJ 2000;162:1343
Canadian researchers have discovered a genetic mutation that appears to double carriers' risk of suicide (Am J Med Genet 2000;96:56-60). The finding could be a significant first step toward developing a test to identify at-risk people and improving prevention and treatment.
In a study involving 251 patients, Dr. Pavel Hrdina and colleagues from the University of Ottawa's Institute of Mental Health Research (IMHR), found that a mutation in the gene encoding the serotonin 5-HT2A receptor was much more common in patients with major depression and suicidal tendencies. Serotonin has long been recognized by scientists as playing a major role in mood regulation, depression and suicide.
"Ours is one of the first demonstrations that a variant of a gene encoding a neurotransmitter receptor is associated with clinical signs of suicidal behaviour," says Hrdina, director of the neuropharmacology lab at IMHR. "This is a small step toward understanding the genetic basis of suicidal behaviour and identifying the contribution that various genes may make to a complex behavioural syndrome such as suicide." The Canadian researchers believe the genetic variation also may help explain the higher incidence of suicide among people with schizophrenia.
Hrdina, along with Drs. Lisheng Du and David Bakish, analysed DNA in blood samples drawn from 131 people with no mental illness and 120 patients with major depression, 78 of whom were suicidal. They found the genetic mutation in 41% of suicidal patients and 24% of non-suicidal patients with depression, but in just 18% of the healthy control group.
The team has shown only that a variant of a gene encoding for a seratonin receptor is significantly associated with increased risk of suicidal behaviour in patients with depression, cautions Hrdina. "We did not show the existence of a 'suicide gene.' It is unlikely that any single gene will be a causative factor." Because the study focused on people with major depression, its findings cannot be generalized to otherwise healthy individuals who attempt to take their life as an isolated call for help or attention, say the researchers.
Replicating and confirming the team's results, and identifying other genes linked to increased risk of suicide, would pave the way for a genetic marker test. Treating those individuals who test positive for the genetic variation, says Hrdina, could prevent unnecessary loss of life. — Greg Basky, Saskatoon
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