A new review has found evidence that a specific gene is linked to suicidal behavior, which may be one of the many complex causes of suicide. 

In the past, studies have implicated the gene for brain-derived neurotrophic factor (BDNF) in suicidal behavior. BDNF is involved in the development of the nervous system. After pooling results from 11 previous studies and adding their own study data involving people with schizophrenia, scientists writing in the International Journal of Neuropsychopharmacology  found that among people with a psychiatric diagnosis, those with the methionine ("met") variation of the gene had a higher risk of suicidal behavior compared to those with the valine variation. 

The review included data from 3,352 people, of whom 1,202 had a history of suicidal behavior. As the low-functioning BDNF met variation is a risk factor for suicidal behavior, it may also be possible to develop a compound to increase BDNF functioning. 

About 90 percent of people who have died by suicide have at least one mental health disorder, the researchers note. Within the studies they reviewed, participants had schizophrenia, depression, bipolar disorder or general mood disorders. In each case, the researchers compared the genotypes of people who had attempted or completed suicide with those who were non-suicidal.

"Our findings may lead to the testing and development of treatments that target this gene in order to help prevent suicide," says Dr. James Kennedy, director of Centre for Addiction and Mental Health's Neuroscience Research Department. "In the future, if other researchers can replicate and extend our findings, then genetic testing may be possible to help identify people at increased risk for suicide." 

Obviously there is no suicide gene and when assessing a person's suicide risk, it's necessary to consider other factors, including early childhood or recent trauma, the use of addictive drugs or medications - and then some people are just depressed or even crazy.