The most significant difference was the size of the thalamus, a small connecting part of the brain which relays sense and motor function information to the cerebral cortex.
The research found the left and right thalamic regions in the brains of people who had attempted suicide were smaller than in people in the other two groups.
It also found the right pallidum and lower surface area of the left inferior parietal lobe were smaller in the group who had carried out suicidal action.
An estimated 800,000 people die globally each year due to suicide, according to the Word Health organisation, while the number who attempt suicide is considered to be higher still.
In Australia, more than 3000 people every year die by suicide, according to the Australian Institute of Health and Welfare, and it was the leading cause of death of young people aged 15 to 19 in 2019.
Study senior co-author Lianne Schmaal from the University of Melbourne said suicidal behaviour was extremely complex, but studies like theirs gave scientists greater insight into the complex interplay of biological and social factors which could lead someone to try to take their own life.
“If we can expand research into the driving mechanisms of suicide, we can hopefully help reduce its personal and societal burden,” Professor Schmaal said.
Lead researcher Adrian Campos said the findings were significant because the study was the first large-scale global study to look at the issue of links between brain structure and suicidal action.
“Previous studies have had quite small sample sizes, but by examining the brains of almost 19,000 people from Europe, North America, Asia and Australia, we could provide strong statistical evidence of the role of brain structure in suicidal behaviour,” he said.