Researchers believe they have identified key networks in the brain that interact to increase the risk that someone will think about – or attempt – suicide.
But they say more research into suicide is urgently needed.
Around 800,000 people die globally by suicide every year, and it is the second leading cause of death among 15 to 29-year-olds.
Dr Anne-Laura van Harmelen, co-first author from the University of Cambridge, said: “Imagine having a disease that we knew killed almost a million people a year, a quarter of them before the age of 30, and yet we knew nothing about why some individuals are more vulnerable to this disease.
“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.”
Scientists carried out a review of two decades’ worth of scientific literature relating to brain imaging studies of suicidal thoughts and behaviour.
They looked at 131 studies, which covered more than 12,000 individuals, analysing changes in brain structure and function that might increase an individual’s suicide risk.
The researchers looked for evidence of structural, functional, and molecular alterations in the brain that could increase risk of suicide.
According to the study published in Molecular Psychiatry, they identified two brain networks – and the connections between them – that appear to play an important role.
One network 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.
Scientists say alterations in this network may lead to excessive negative thoughts and difficulties regulating emotions, stimulating thoughts of suicide.
The second network they identified involves regions known as the dorsal prefrontal cortex and inferior frontal gyrus system.
Alterations in this network may influence suicide attempt, in part, due to its role in decision making, generating alternative solutions to problems, and controlling behaviour, researchers say.
They suggest that if both networks are altered in terms of their structure, function or biochemistry, this may lead to situations where an individual thinks negatively about the future and is unable to control their thoughts.
This might lead to situations where they are at higher risk for suicide, the study suggests.
Hilary Blumberg, John and Hope Furth Professor of psychiatric neuroscience at Yale, said: “The review provides evidence to support a very hopeful future in which we will find new and improved ways to reduce risk of suicide.
“The brain circuitry differences found to converge across the many studies provide important targets for the generation of more effective suicide prevention strategies.
“It is especially hopeful that scientists, such as my co-authors on this paper, are coming together in larger collaborative efforts that hold terrific promise.”
Scientists say there is an urgent need for more research looking at whether their proposed model relates to future suicide attempts and at whether any therapies could change the structure or function of these brain networks and thereby perhaps reduce suicide risk.
Co-first author Dr Lianne Schmaal, from the University of Melbourne, said: “The biggest predictor of death by suicide is previous suicide attempt, so it’s essential that we can intervene as early as possible to reduce an individual’s risk.
“For many individuals, this will be during adolescence. If we can work out a way to identify those young people at greatest risk, then we will have a chance to step in and help them at this important stage in their lives.”