Brain scans may be able to identify people at risk of attempting suicide, say scientists who have discovered a chemical linked to suicidal thoughts in people with post-traumatic stress disorder (PTSD).
The risk of suicide among individuals with PTSD is much higher than the general population, but identifying those individuals at greatest risk has been difficult.
Researchers at Yale University in the US used PET imaging to measure levels of metabotropic glutamatergic receptor 5 (mGluR5) -- which has been implicated in anxiety and mood disorders -- in individuals with PTSD and major depressive disorder.
The study, published in the journal Proceedings of the National Academy of Sciences, found high levels of mGluR5 in the PTSD group with current suicidal thoughts.
The team found no such elevated levels in the PTSD group with no suicidal thoughts or in those with depression, with or without current suicidal thoughts.
There are two approved treatments for PTSD, but it can take weeks or months to determine whether they are effective, researchers said. That can be too late for those who are suicidal.
"If you have people who suffer from high blood pressure, you want to reduce those levels right away," said Irina Esterlis, associate professor at Yale.
"We don't have that option with PTSD," Esterlis said in a statement.
Esterlis said testing for levels of mGluR5 in people who have experienced severe trauma might help identify those at greatest risk of harming themselves and prompt psychiatric interventions.
Regulating levels mGluR5 could also minimise suicide risk in PTSD patients, Esterlis said.