Researchers have used brain scanning technology to confirm a relationship between levels of a common type of receptor and the risk for suicidal thinking in people with post-traumatic stress disorder (PTSD). The discovery could help scientists develop a test for suicide risk in PTSD patients, as well as a potential new way to treat PTSD.

A team led by 2012 and 2007 BBRF Young Investigator Irina Esterlis, Ph.D., of Yale University, has reported in Proceedings of the National Academy of Sciences that brain levels of a receptor called mGlur5 are “significantly” elevated in people with PTSD who are contemplating suicide. BBRF Scientific Council member and three-time BBRF grantee John Krystal, M.D., was also on the team. “Currently there is not an approved treatment to relieve suicidal thinking in PTSD,” Dr. Esterlis noted.

mGluR5 is a very common receptor—a docking port for other molecules—found throughout the brain. Involved in emotional learning, memory, and other functions, it helps to regulate the neurotransmitter glutamate, the equally ubiquitous neurotransmitter that propagates excitatory messages among neurons.

Levels of mGluR5 were measured in five brain areas (frontal and limbic) in PET scans of three groups of 29 individuals: one group whose members had PTSD and in some cases major depression, too; one whose members had only major depression; and one composed of healthy controls.

Major depression and PTSD often occur together. Both are associated with elevated suicide risk—suicidal ideation or thinking about suicide; suicide attempts; and death by suicide.

Dr. Esterlis and colleagues made several important findings based on the PET scans. They specifically noted a correlation of high mGluR5 levels with suicidal ideation among subjects who had such thoughts the same day they received their scan. This suggests that mGluR5 in the scanned regions is a candidate biomarker for suicide risk in patients with PTSD.

PTSD patients without suicidal ideation did not have significantly elevated mGluR5 levels in the scanned regions. Also, mGluR5 levels were not found to be significantly different in a comparison of people with major depression and controls.

Together, these findings suggested to the team the potential value of mGluR5 as a biomarker of suicide risk in people with PTSD. The fact that it does not appear to be a marker of such risk in major depression may indicate that there are multiple biological pathways to suicidal behavior.

Noting that mGluR5 levels were also correlated with certain PTSD symptoms involving mood and anxiety, including avoidance, the researchers speculated that pharmaceuticals capable of lowering mGlur5 levels in the brain might one day help treat PTSD.

Noting that mGluR5 levels were also correlated with certain PTSD symptoms involving mood and anxiety, including avoidance, the researchers speculated that pharmaceuticals capable of lowering mGlur5 levels in the brain might one day help treat PTSD.

Jeffrey Borenstein, M.D., BBRF’s President and CEO, commented on the team’s discoveries, in an article on HealthDay.com.