Since 2017, an international team, led by the University of Edinburgh and King's College in London and including researchers from QIMR Berghofer, The University of Queensland (UQ) and the Brain and Mind Centre in Sydney, analysed data from 29 countries across the world. This included genetic samples from 680,000 people with depression and four million people who had not experienced depression. Notably, one in four participants were from a non-European background. The team found a total of 697 genetic variants linked to depression, a remarkable increase on what was previously known.
Each genetic variant has a very small effect on the overall risk of someone developing depression. If a person has multiple variants, these small effects can add up, increasing their risk.
QIMR Berghofer researcher Dr Brittany Mitchell
QIMR Berghofer researcher Dr Brittany Mitchell said our current limited understanding of depression made it hard to improve outcomes for those affected.
"While depression is a growing major health issue, we lack the insights needed to better treat and prevent it," she said.
"Larger, more inclusive studies like this will help us develop better treatments and interventions, ultimately improving lives and reducing the global impact of the condition. It will also reinforce the evidence that mental health conditions are as biologically based as other conditions like heart disease."
Australia's contribution to the international study was vital.
More than 50 of the newly identified gene variants came via results from the Australian Genetics of Depression Study (AGDS) which provided a database of 16,000 participants with depression and 18,000 without depression providing saliva samples for analysis.
UQ scientist and AGDS study co-lead analyst Dr Enda Byrne said the findings were a step forward to understanding depression at a biological level.
"Our research has identified numerous genetic factors that contribute to the condition, showing that it involves a complex mix of genes. These findings offer new opportunities to improve how we treat and support those with depression," he said.
The researchers said the findings also represented an opportunity to re-think current medical treatments for depression.
It is understood that drugs used to treat chronic pain and the sleep disorder narcolepsy could potentially be repurposed for the treatment of depression, based on the study findings.
However, the research team cautioned that further studies and clinical trials were needed to explore the potential of the drugs in patients with depression.
The Australian contribution to the study, which is published in the journal Cell was funded by the National Health and Medical Research Council.
The research team from the Psychiatric Genomics Consortium involved scientists from continents including the UK, South Africa, Brazil, Mexico, the USA, Australia, Taiwan and China.
