BIOMARKERS in the blood can be used to identify people at risk of suicide, a study suggests.
The US research raises the controversial prospect of a blood test providing early warning of suicide attempts.
Scientists said their results were “proof of principle” for a suicide test, but British experts reacted with scepticism.
An enzyme called SAT1 was linked to suicidal tendencies in a group of patients with bipolar disorder, a mental illness characterised by extreme high and low moods. Three other markers showed a weaker association.
The elevated blood markers stood out in a subgroup of nine patients who displayed a sudden dramatic shift to powerful suicidal thoughts. A similar pattern was seen in blood samples from nine suicide victims who had succeeded in killing themselves.
Finally, blood samples were tested from two further groups of patients with bipolar disorder and schizophrenia-type psychoses. Raised levels of the biomarkers correlated with admissions to hospital after suicide attempts. The link was stronger for bipolar disorder than for schizophrenia.
Dr Alexander Niculescu, who led the study at Indiana University, said: “There are people who will not reveal they are having suicidal thoughts when you ask them, who then commit it and there’s nothing you can do about it. We need better ways to identify, intervene and prevent these tragic cases.
“These seem to be good markers for suicidal behaviour in males who have bipolar mood disorders or males in the general population who commit impulsive, violent suicide.
“In the future, we want to study and assemble clinical and socio-demographic risk factors, along with our blood tests, to increase our ability to predict risk.”
He acknowledged one limitation of the research, published in the journal Molecular Psychiatry, was that the participants were all male.
British scientists said the research should be treated with caution. Professor Keith Hawton, director of the Centre for Suicide Research at Oxford University, said: “There is a big difference between finding differences between groups [as in this study] compared with risk in actual individuals, the latter being the real test of predictors.”
Professor Matthew Hotopf, from the Institute of Psychiatry at King’s College London, stressed the need to have the results replicated by other studies.
He added: “It’s one thing to find a biomarker which might be associated at a statistical level with suicide or suicidal behaviour. It’s quite another to use it to make any kind of prediction which has clinical utility.
“These findings may attract media attention, but they are preliminary and my money would be on failed replication, and even if replication was successful, lack of predictive power to be a useful clinical tool.”