Depression can play a direct role in the development of type 2 diabetes, according to research that experts say could help boost efforts to prevent the condition.
Researchers have found a causal relationship and shared genetics suggesting depression may be a cause of type 2 diabetes, a disease with which more than 500 million people worldwide live.
The discovery has prompted calls for depression to be considered a risk factor for type 2 diabetes alongside other risk factors such as obesity, inactivity and a family history of the condition.
The researchers suggest people with a history of depression should be assessed for their risk of type 2 diabetes so they can be supported to avoid developing the condition.
Experts have known for years that people with type 2 diabetes are about twice as likely to suffer depression compared with those without. It is also well established that people with depression have a higher risk of developing type 2.
However, until now it has been unclear whether depression caused type 2 or vice versa, or whether other factors are at play. In the latest study, researchers found for the first time that depression directly causes an increased risk of developing type 2, but did not find that diabetes causes depression. The findings were published in the journal Diabetes Care.
Dr Elizabeth Robertson, the director of research at Diabetes UK, which funded the study, said: “This hugely important study gives us new insights into the links between genetics, type 2 diabetes and depression, indicating that depression can contribute to the development of type 2 diabetes. Type 2 diabetes is complex, with multiple risk factors – and previous research has shown that the condition is more common in people with depression.
“This study gives us greater insight into why and indicates that depression should now be considered a risk factor for type 2. This knowledge could help healthcare professionals to improve care and support for people with a history of depression and prevent more cases of type 2 diabetes.”
The study used data from hundreds of thousands of people in the UK and Finland, including 19,000 people with type 2, 5,000 diagnosed with depression and 153,000 who self-reported depression.
Researchers used a statistical method called Mendelian randomisation to analyse genetic and health information. They found that only 36.5% of the effect of depression on type 2 diabetes could be explained by obesity. Obese people are significantly more likely to have type 2 than those of a healthy weight.
The researchers also noted seven genetic variants that contribute to both type 2 diabetes and depression. These shared genes play a role in insulin secretion or inflammation in the brain, pancreas or fat tissue, with changes in these biological processes potentially explaining how depression increases type 2, they suggested.
And while a direct cause was not found for diabetes causing depression, experts still believe that the burden of living with type 2 diabetes may be a factor in developing depression.
“We strongly encourage anyone with depression to know their risk of type 2 diabetes by completing Diabetes UK’s free online know your risk tool, so they can get the right support to reduce their risk and avoid type 2 diabetes,” said Robertson.
Prof Inga Prokopenko, of the University of Surrey, who led the study, said: “Our discovery illuminates depression as a contributing cause of type 2 diabetes and could help to improve prevention efforts.
“The findings are important for both individuals living with the conditions and healthcare providers, who should consider implementing additional examinations to help prevent type 2 diabetes onset in people suffering from depression.”
