New QIMR Berghofer-led research has identified 509 genes that influence both depression and anxiety, confirming a genetic relationship between the mental health conditions.
The study findings have been published in the prestigious journal Nature Human Behaviour, and are the first to identify so many genes that are shared between depression and anxiety.
The senior researcher and head of QIMR Berghofer’s Translational Neurogenomics Group, Professor Eske Derks, said depression and anxiety are the two most prevalent psychiatric disorders in the world and often co-occur together in the same person.
“Not a lot has been known, until now, about the genetic causes of why people may suffer from depression and anxiety. Both disorders are highly comorbid conditions, with about three-quarters of people with an anxiety disorder also exhibiting symptoms of major depressive disorder,” Professor Derks said.
“We identified 674 genes associated with either depression or anxiety – and importantly about three quarters of those genes were shared.
“Our research provides new insights into the genetic architecture of depression and anxiety and the genes that link them.
“The better our understanding of the genetic basis of these psychiatric conditions, the more likely we are to be able to treat them.
“It’s been observed in the past that people who have both depression and anxiety have more severe symptoms, have the illnesses for longer and are more resistant to treatments. We hope this study will help identify existing drugs that might be re-purposed to better target the genetic basis of depression and anxiety.”
The research team examined genomic data from more than 400,000 participants in the UK Biobank who reported their symptoms of depression and anxiety. The team then replicated and validated the genetic results in an independent group of 1.9 million people who had self-reported whether they had been diagnosed with depression or anxiety to a personal genomic and biotechnology company.
Lead researcher from QIMR Berghofer’s Translational Neurogenomics Group Jackson Thorp worked on the genetic study as part of his PhD.
He said they examined the genetic relationship between 28 individual symptoms related to depression and anxiety to understand how they overlapped.
“These kinds of complex disorders are influenced by large numbers of genes, with each having a small individual effect, which is why we needed a very large sample size to get a clear picture of the genetic influences on these disorders,” Mr Thorp said.
“While many genes are shared between anxiety and depression, we also found genes that are specific to each disorder.”
Mr Thorp said some of the genes that are unique to depression were linked to higher levels of the fat triglyceride in the blood – a condition called hypertriglyceridemia.
“The link between those depression-specific genes and hypertriglyceridemia suggests there may be a metabolic component of depression that is not as strong in anxiety,” Mr Thorp said.
“Conversely, our results showed that some of the genes specific to anxiety were related to blood pressure, which is consistent with previous research that has shown a link between the disorder and hypertension.”
In an extension of the study the researchers then explored in what regions of the human genome the genes were located to identify regions that had not previously been linked to the disorders.
“Our research identified 71 regions that were not previously associated with anxiety, which is a significant increase from the six regions that had been identified for the disorder before,” Mr Thorp said.
“We also identified 29 new regions associated with depression.”
Professor Derks said the researchers hoped to expand their study to find even more genomic regions that are yet to be identified as genetic causal risk factors of these two disorders and other psychiatric illnesses.
The research findings can be accessed on the Nature Human Behaviour website.
The study was primarily funded by QIMR Berghofer and Mr Thorp’s scholarship by The University of Queensland.
The World Health Organization (WHO) estimates that 4.4 per cent of the global population suffers from a depressive disorder, and 3.6 per cent from an anxiety disorder. It says many people experience both conditions simultaneously (comorbidity), so it is inappropriate to simply add the two figures together to arrive at a total for common mental disorders.
The WHO defines depressive disorders as characterised by sadness, loss of interest or pleasure, feelings of guilt or low self-worth, disturbed sleep or appetite, feelings of tiredness, and poor concentration. It can be long lasting or recurrent and substantially impair an individual’s daily life.
The WHO defines anxiety disorders as a group of mental disorders characterised by feelings of anxiety and fear, including generalised anxiety disorder (GAD), panic disorder, phobias, social anxiety disorder, obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD). As with depression, symptoms can range from mild to severe.