Scientists have pinpointed nearly 80 genes which they believe could help explain why some people are more susceptible to depression.
A team of experts led by the University of Edinburgh analysed the genetic codes of 300,000 people to identify areas of DNA which may be linked to the condition.
They found 78 genes which could help explain what triggers depression and assist with the development of better treatments.
Dr David Howard, lead author of the report, said: "This study identifies genes that potentially increase our risk of depression, adding to the evidence that it is partly a genetic disorder.
"The findings also provide new clues to the causes of depression and we hope it will narrow down the search for therapies that could help people living with the condition."
Depression affects one in five people in the UK every year and is the leading cause of disability worldwide.
Life events such as trauma or stress can contribute to its onset but it has not been clear why some are more likely to develop the condition than others.
The scientists used information from a UK Biobank - a research resource containing health and genetic information for 500,000 people - to conduct their study.
Some of the genes discovered are known to be involved in the function of synapses, tiny connectors that allow brain cells to communicate with each other through electrical and chemical signals.
They then confirmed their findings by examining anonymised information held by personal genetics and research company 23andMe, with the donors' consent.
Professor Andrew McIntosh, who leads the Edinburgh-based research group, said: "Depression is a common and often severe condition that affects millions of people worldwide.
"These new findings help us better understand the causes of depression and show how the UK Biobank study and big data research has helped advance mental health research.
"We hope that the UK's growing health data research capacity will help us to make major advances in our understanding of depression in coming years."
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