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Brain Chemical Linked to Suicidal Behavior

Blocking effects of glutamate could prevent suicides (Dec. 13)

Researchers at the University of Michigan have found the first evidence that glutamate, a chemical in the brain, is linked to suicidal behavior, offering new hope for efforts to prevent people from taking their own lives.

In a paper published in Neuropsychopharmacology, Dr. Lena Brundin and colleagues report that glutamate is more active in the brains of people who attempt suicide. Glutamate is an amino acid that sends signals between nerve cells and has long been a suspect in the search for chemical causes of depression.

“The findings are important because they show a mechanism of disease in patients,” Brundin said. “There’s been a lot of focus on another neurotransmitter called serotonin for about 40 years now. The conclusion from our paper is that we need to turn some of that focus to glutamate.”

Brundin and colleagues examined glutamate activity by measuring quinolinic acid — which causes glutamate to send more signals to nearby cells — in the spinal fluid of 100 patients in Sweden. About two-thirds of the participants were admitted to a hospital after attempting suicide, and the rest were healthy.

The researchers found that the patients who attempted suicide had more than twice as much quinolinic acid in their spinal fluid as did the healthy people, which indicated increased glutamate signaling between nerve cells. The patients who reported the strongest desire to kill themselves also had the highest acid levels.

The results also showed decreased levels of quinolinic acid in a subset of patients who came back 6 months later, when their suicidal behavior had ended.

The new findings explain why earlier research has pointed to inflammation in the brain as a risk factor for suicide. The body produces quinolinic acid as part of the immune response that creates inflammation. Brundin said anti-glutamate drugs are still in development but could soon offer a promising tool for preventing suicide. In fact, recent clinical studies have shown that the anesthetic ketamine — which inhibits glutamate signaling — is effective in treating depression, although the drug’s side effects prevent it from being widely used.

In the meantime, Brundin said, physicians should be aware of inflammation as a likely trigger for suicidal behavior.

Source: University of Michigan; December 13, 2012.

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