Females carry a much higher genetic risk of major depression than males, new research has found.
In the largest study of its kind involving about 200,000 people diagnosed with depression in Australia, Europe, the UK and US, scientists identified almost twice as many genetic red flags for depression in the DNA of females compared with males.
They identified about 7,000 changes in the DNA that could cause major depressive disorder in both sexes, and about 6,000 more that could cause the mental illness in females only.
The scientists hope their work, published in the journal Nature Communications, will eventually pave the way for more personalised treatments.
Research has consistently found women are twice as likely to experience depression during their lives than men.
Males and females also experienced depression differently, the study authors wrote in the paper.
Females were more likely to have symptoms such as weight gain, excessive daytime sleepiness and increased appetite, while males more frequently exhibited anger, aggression, risk-taking behaviours and substance abuse, they said.
Dr Jodi Thomas says the impact of environmental influences on depression will be of interest for future research. (Supplied: QIMR Berghofer)
Neuro-geneticist Jodi Thomas, of QIMR Berghofer, who led the study, said the scientists found genetic factors linked to depression overlapped more with those associated with metabolic traits in females.
“That’s an interesting finding that we can … continue on the road and see if perhaps therapeutics that are targeting more of these shared signals between depression and metabolic traits may be very good treatments for females,” Dr Thomas said.
“I think this study is really cool in that it demonstrates that we do find a lot of interesting findings, and new findings, when we separate our participants into females and males.”
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Dr Thomas said the genetic findings did not discount the role of different life experiences among males and females in the development of major depression, such as the increased risk of sexual abuse in females.
“We know that depression is caused not only by genetics, it also has a very large environmental influence,” she said.
“We didn’t look into that in this research, but it definitely is something that will be of interest for future research.”
The researchers have made their results publicly available, allowing other scientists to analyse them further.
QIMR Berghofer researchers Dr Brittany Mitchell (left) and Dr Jodi Thomas found about twice as many genetic flags for depression in the DNA of females compared to males. (Supplied: QIMR Berghofer)
Dr Thomas and her colleague Dr Brittany Mitchell, a senior researcher at QIMR Berghofer’s Genetic Epidemiology Laboratory, who was also involved in the study, hope it will lead to similar research involving other health conditions where a person’s sex is considered.
“Traditionally, a lot of research, particularly on health conditions, has really focused on males,” Dr Thomas said.
“This leaves a really big gap in our understanding of female health.”
Study helps lay ‘groundwork’ for diagnosis and treatment
The researchers analysed the DNA of about 130,000 female participants with major depression and almost 65,000 males diagnosed with the mental health disorder.
They compared the data to almost 160,000 females and more than 132,000 males without a depression diagnosis.
Dr Thomas said they performed different analyses to confirm their findings were sound.
Dr Thomas led the research into genetic links. (Supplied: QIMR Berghofer)
She said their study accounted for the fact males were less likely to seek professional help or disclose depressive symptoms, leading to underdiagnosis.
Clinical psychologist Luke Martin, who was not involved in the study, said the research made a “unique contribution around the sex differences and the potential increased genetic loading that females might carry for depression”.
Dr Martin, who is a spokesperson for mental health support organisation Beyond Blue, said depression was a “very complex puzzle” and the study helped “put more of those pieces together”.
“We know that when it comes to mental health we’re really looking at a range of biological, psychological and social causes and we need to consider all of them when thinking about why someone might experience depression,” he said.
How scientists’ discovery of genetic links to depression could make treatment more personal
He said while existing treatments for depression “work for a lot of people”, they were not effective for everyone.
“These kinds of studies do lay the scientific groundwork for us to be more precise in how we diagnose and treat depression,” Dr Martin said.
He said while genes played a role in depression, they were not “deterministic”.
“If you have a genetic loading for depression, it doesn’t mean that you’re definitely going to get depression, it just means that you have an increased risk,” Dr Martin said.
Individuals could reduce their likelihood of experiencing depression by staying socially connected, moving their bodies, eating well, interpreting situations “in healthy and balanced ways”, and having meaning and purpose in life every day, he said.
“There’s really strong evidence that does reduce our risk for depression,” Dr Martin said.
