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Blood marker may predict suicide

People who killed themselves had higher levels of specific gene

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A substance that has been found at elevated levels in the blood of people likely to kill themselves could lead to a simple diagnostic test for suicide risk, researchers report August 20 in Molecular Psychiatry.

Right now, clinicians rely on people’s self-reported symptoms and feelings to decide who is in need of immediate help, but a person intent on suicide isn’t always forthcoming. An unambiguous blood test would show clinicians who is in immediate danger.

“There is such a need for markers,” says study coauthor Alexander Niculescu of Indiana University School of Medicine. “We need to advance this research very fast.”

Outside researchers are quick to say that the study should be interpreted cautiously. Nonetheless, the findings are “amazingly strong for a small sample size,” says psychiatrist J. John Mann of Columbia University and the New York State Psychiatric Institute.

The results came out of a larger study on men with bipolar disorder. As part of that research, subjects would visit a clinic every three to six months, where they would undergo psychological testing and give a blood sample. Over the course of the study, nine men showed a dramatic change between visits, first exhibiting no signs of suicidal tendencies and later exhibiting many.

Several biological molecules in the blood of these people changed along with this suicidal shift. Most notable was a molecule made by the gene SAT1, which is involved in cell death. For these nine men, high SAT1 activity tracked with more suicidal thoughts and feelings, the team found. 

To see if SAT1 might track with suicide more generally, the team obtained blood samples from a coroner’s office. SAT1 activity was found to be high in the blood of nine different men who had killed themselves. “To our surprise, the results were very strong,” Niculescu says.

SAT1 levels were also tied to hospitalizations for suicidal behavior, the team found. In 49 different bipolar men, those with higher SAT1 levels were more likely to be admitted than people with low levels. Researchers don’t know why SAT1 levels are correlated with suicide risk in this population.

“This is a very interesting area and a very important question, but there are a lot of technical issues with this study,” says neuroscientist Carl Ernst of McGill University in Montreal. “There’s not a lot we can take from it at this stage.”

The study followed a small number of men who were all on various medications. What’s more, the algorithm used to identify SAT1 and other markers is somewhat subjective, and it’s unclear whether men with bipolar disorder are a good proxy for suicidal people in general, Ernst says. SAT1 levels may have nothing to do with suicide in women or in people with major depressive disorder, for instance.

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