The international research, led by researchers at Queensland's QIMR Berghofer Medical Research Institute, found the structures of three key brain regions were different in people with depression who had attempted suicide and those who hadn't.

Senior researcher Dr Miguel E Renteria says the findings suggest that people who had attempted to end their lives had a slightly smaller thalamus and right pallidum, as well as lower surface area of the left inferior parietal lobe.

"Our research provides a better understanding of the biological basis of suicidal behaviour, and is an important first step towards developing more effective and targeted suicide prevention and intervention strategies and treatments in the future," she said in a statement on Friday.

The study, involved 60 researchers examining brain imaging and clinical data from almost 19,000 people, including 694 people who had attempted suicide, 6448 people diagnosed with depression who had not attempted suicide, and 12,477 healthy control patients.

University of Melbourne Associate Professor Lianne Schmaal, one of the study's senior co-authors, said it's still not certain what causes the structural change in people's brains.

However, she said it highlights three areas of the brain that researchers needed to understand better.

"Suicidal behaviour is varied and complex, and is a considerable health concern in both developed and developing countries. It is more common in people living with mental illness,," Associate Professor Schmaal said.

"If we can expand research into the driving mechanisms of suicide, we can hopefully help reduce its personal and societal burden."

The QIMR Berghoher said close to 800,000 people worldwide die by suicide every year, according to the World Health Organisation, and for every suicide there are many more people who attempt to take their own lives.

Suicide was the third leading cause of death in 15-19-year-olds globally in 2016.

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Australian Associated Press