Biomarkers for suicide

Scientists are trying to develop a blood test that would identify people at greatest risk of committing suicide. A new study identifies two key biomarkers. (Michael Robinson Chavez / August 20, 2013)

A blood test can tell you if you’ve got HIV, high cholesterol or certain kinds of cancer. Now scientists are trying to create a blood test that would reveal whether someone was about to commit suicide.

“Individuals at risk often choose not to share their ideation or intent with others, for fear of stigma, or that in fact their plans may be thwarted,” the researchers explained in their study, published online Tuesday by the journal Molecular Psychiatry. “Given the fact that approximately 1 million people die of suicide worldwide each year, and this is a potentially preventable cause of death, the need for, urgency and importance of efforts such as ours cannot be overstated.”

The basic idea is to find biomarkers in the blood that are particularly high or low in people who are on the verge of killing themselves compared with people who are not. In this case, the researchers focused on gene expression biomarkers -- molecules in the blood that show how active certain genes are.

And they’ve got some promising leads. High expression of a gene called SAT1 had strong links to suicidal thinking. So did low expression of a gene called CD24.

The research team, led by scientists from the Indiana University School of Medicine and the VA Medical Center in Indianapolis, started off with a group of white men with bipolar disorder who checked in with researchers every three to six months. Each time, they gave blood samples and answered questions about their psychiatric states, including one about suicidal thoughts.

In nine cases, scores for suicidal thinking switched from low to high. Those nine patients had a total of 24 visits with researchers. The scientists compared blood samples drawn when patients’ suicidal thoughts were low to blood samples drawn when suicidal thoughts were high. SAT1 and CD24 emerged as two biomarkers that moved in tandem with suicide risk.

Next, the researchers worked with the Marion County Coroner’s Office in Indianapolis to examine blood samples taken from nine men who had killed themselves without overdosing on drugs (drugs might change the mix of biomarkers in their blood). In all nine cases, expression of the SAT1 gene was unusually high -- much higher than the levels seen in people with suicidal thoughts who didn’t kill themselves.

As an additional test, the researchers turned to two more groups of patients -- one group made up of people with bipolar disorder, and the other of people with schizophrenia or schizoaffective disorder, a form of psychosis. Among the bipolar patients, there was a link between high SAT1 levels and hospitalization for suicidal behavior. Among the psychosis patients, the pattern was present but weaker.

In summarizing their findings, the researchers wrote that more work was needed not just to see whether measurements of SAT1 and CD24 can flag people who are most at risk of committing suicide, but also to see whether these two genes have the same predictive value for patients who aren’t white men.

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