Could a genetic test predict the risk for suicide?

 While claims for a suicide test remain preliminary, and controversial, a "suicide gene" is not as fanciful as it sounds, writes Antonio Regalado.

When someone commits suicide, the reaction is often the same. It’s disbelief, mixed with a recognition that the signs were all there. Depression. Maybe talk of ending one’s life.

Now, by studying people who think about committing suicide, as well as the brains of people who actually did, two groups of genome researchers in the U.S. and Europe are claiming they can use DNA tests to actually predict who will attempt suicide.

While claims for a suicide test remain preliminary, and controversial, a “suicide gene” is not as fanciful as it sounds. The chance that a person takes his or her own life is in fact heritable, and many scientific teams are now involved in broad expeditions across the human genome to locate suicide’s biological causes. Based on such gene research, one startup company, Sundance Diagnostics, based in Boulder, Colorado, says it will begin offering a suicide risk test to doctors next month.

The Sundance test rests on research findings reported by the Max Planck Institute of Psychiatry in 2012. The German researchers, based in Munich, scanned the genes of 898 people taking anti depressants and identified 79 genetic markers they claimed together had a 91 per cent probability of correctly predicting “suicidal ideation,” or imagining the act of suicide.

It’s well known that after going on antidepressants, some people do begin thinking about killing themselves. “The number of completed suicides is not large, but none of us want our loved one to be at risk,” said Sundance CEO Kim Bechthold, who licensed the test idea from Max Planck. She says the DNA tests will be carried out on a saliva sample.

Is there a suicide gene?

Given how many people take antidepressants, the market for a suicide test could be big. For now, however, experts say there are good reasons to view any suicide test with skepticism. Genome studies often turn up apparent connections that later are found not to mean much. Dozens of genes have been linked to suicide, but none in a truly definitive fashion.

“I don’t think there are any credible genomic tests for suicide risk or prevention,” said Muin J Khoury, head of the Office of Public Health Genomics at the US Centers for Disease Control and Prevention. What is certain, is that suicide runs in families. On its list of suicide risk factors, the CDC lists family history as the most important, followed by mistreatment of children, prior suicide attempts and depression.

Epidemiologists believe that 30 per cent to 55 per cent of the risk that someone takes their own life is inherited, and the risk isn’t linked to any specific mental illness, like depression or schizophrenia.
That means suicide probably has its own unique genetic causes, said Stella Dracheva, a pathologist who studies the brains of suicide victims at the Icahn School of Medicine at Mount Sinai Hospital in New York. In her view, that means it’s worth searching for suicide genes and that a DNA test is also theoretically plausible.

The pain and disbelief surrounding suicide only raises the stakes for scientists claiming they can predict it. The latest report of a possible suicide test came from Johns Hopkins University where geneticists published a report saying that the presence of alterations to a single gene could predict who will attempt suicide with 80 per cent accuracy.

Definitive tests in progress

Johns Hopkins has filed a patent on a suicide test, and the university is attempting to license it. The research, carried out by Zachary Kaminsky, an assistant professor of psychiatry at Johns Hopkins, began on a collection of a small number of brains of suicide victims held by the National Institutes of Health.

Instead of looking just at DNA, they studied patterns of methylation, a type of chemical block on genes that can lower their activity. They found that one gene, SKA2, seemed to be blocked often in the suicide brains. They later found the same gene block was common when they tested the blood of a larger number of people having suicidal thoughts.

Kaminsky said that following the report, his email inbox was immediately flooded by people wanting the test. They didn’t understand that the type of DNA change he identified probably isn’t the inherited kind, but instead may be the result of stress or some other environmental factor.

The same publication has drawn some criticism from scientists who say his conclusions were based on thin evidence. “It’s a striking finding, but as always, when you look at complex genetics, you need replication,” said Willour. The bigger problem, said Dracheva, is that there are simply not enough brains of suicide victims to study. Unlike studies of diabetes or schizophrenia, where scientists can call on thousands or tens of thousands of patients, suicide studies remain small, and their findings much more tentative.

It’s because they don’t have DNA from enough people who committed suicide that researchers, including those at Hopkins and Max Planck, have had to try connecting the dots between DNA and whether or not people have suicidal thoughts. “Who doesn’t think about killing themselves?” said Dracheva.