London, Dec 2 : Researchers have identified key networks within the brain which they say interact to increase the risk that an individual will think about - or attempt - suicide.
Combining the results from all of the brain imaging studies available, the researchers looked for evidence of structural, functional and molecular alterations in the brain that could increase the risk of suicide.
They identified two brain networks - and the connections between them - that appear to play an important role.
The first of these networks involves areas towards the front of the brain known as the medial and lateral ventral prefrontal cortex and their connections to other brain regions involved in emotion.
Alterations in this network may lead to excessive negative thoughts and difficulties regulating emotions, stimulating thoughts of suicide, according to the study published in the journal Molecular Psychiatry.
The second network involves regions known as the dorsal prefrontal cortex and inferior frontal gyrus system.
Alterations in this network may influence a suicide attempt, in part, due to its role in decision making, generating alternative solutions to problems and controlling behaviour, said the study.
The researchers suggest that if both networks are altered in terms of their structure, function or biochemistry, this might lead to situations where an individual thinks negatively about the future and is unable to control their thoughts, which might lead to situations where an individual is at higher risk of suicide.
"There are very vulnerable groups who are clearly not being served by research for a number of reasons, including the need to prioritise treatment, and reduce stigma," said Anne-Laura van Harmelen, co-first author from the University of Cambridge.
"We urgently need to study these groups and find ways to help and support them," van Harmelen said.
For the study, the international team of researchers carried out a review of two decades' worth of scientific literature relating to brain imaging studies of suicidal thoughts and behaviour.
In total, they looked at 131 studies, which covered more than 12,000 individuals, looking at alterations in brain structure and function that might increase an individual's suicide risk.
The researchers said that their review of existing literature revealed how little research has been done into one of the world's major killers, particularly among the most vulnerable groups.
The facts in relation to suicide are stark: 800,000 people commit suicide every year, the equivalent of one every 40 seconds.
Suicide is the second leading cause of death globally among 15-29 year olds.
More adolescents commit suicide than dying from cancer, heart disease, AIDS, birth defects, stroke, pneumonia, influenza and chronic lung disease combined.
As many as one in three adolescents think about ending their lives and one in three of these will attempt suicide.
"Imagine having a disease that we knew killed almost a million people a year, a quarter of them before the age of thirty, and yet we knew nothing about why some individuals are more vulnerable to this disease," van Harmelen said.
"This is where we are with suicide. We know very little about what's happening in the brain, why there are sex differences, and what makes young people especially vulnerable to suicide."