A blood test for suicide? US study raises controversial prospect to identify people at risk

US research has raised the controversial prospect of using a blood test to detect thoughts of suicidal thoughts.

For the first time, suicide risk has been linked to biomarkers in the blood by researchers looking into predictors.

Scientists found increased amounts of specific proteins in the blood stream of people who were contemplating suicide.

The study, conducted by researchers at Indiana University, found that an enzyme called SAT1 was linked to suicidal tendencies.

The study involved taking samples from participants over an extended period of time, whilst interviewing them at three to six month intervals.

Seventy-five males with conditions such as bipolar were used as participants as they are at a higher risk of committing suicide than others.

Researchers then tested the samples to look for differences in protein activity.

The increased presence of this specific blood marker was apparent in a subgroup of nine patients who displayed a sudden dramatic shift to powerful suicidal thoughts.

A similar pattern was seen in blood samples taken from nine suicide victims who had succeeded in taking their own lives.

Raised levels of the biomarkers correlated with admissions to hospital after suicide attempts. The link was stronger for bipolar disorder than for schizophrenia.

Researchers in the US now argue their results are "proof of principle" for a suicide test.

Study leader Dr Alexander Niculescu, from Indiana University, said: "Suicide is a big problem in psychiatry. It's a big problem in the civilian realm, it's a big problem in the military realm and there are no objective markers.

"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."

However because the number of participants used in the study was relatively low at 75 and all male, Dr Niculescu said he plans to conduct further research focusing on more deliberate and planned suicides with a bigger and more varied sample. "There could be gender differences," he said.

"We would also like to conduct more extensive, normative studies in the population at large."

"Over a million people each year world-wide die from suicide and this is a preventable tragedy," he added.

In their paper, the scientists point to a link between SAT1 and polyamine, a chemical involved in apoptosis, or "cell suicide" - the programmed self destruction of damaged or harmful cells.

They wrote: "It could be that.. mechanisms related to cellular survival have been recruited by evolution for higher mental functions, such as feelings, thoughts, actions and behaviours, leading to suicidality.

"In that sense, suicidality could be viewed as a whole-organism apoptosis."

Lithium, a treatment for bipolar disorder shown to prevent suicide, suppresses apoptosis at the cellular level, they pointed out.

But British scientists have warned 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.

"I would say that the findings are of interest and may point the way to some future research based on large samples, but no more than that."

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/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 very much 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."

Additional reporting by Press Association