New study reveals depression is a risk factor for type 2 diabetes

The study, led by Professor Inga Prokopenko from the University of Surrey, used genetic data from hundreds of thousands of people in the UK and Finland to shed new light on the complex relationship between depression and type 2 diabetes.    

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.    

Professor Inga Prokopenko, Professor e-One Health and Head of Statistical Multi-Omics from the University of Surrey, 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." 

Previous research has indicated that people with type 2 diabetes are approximately twice as likely to experience depression compared to those without diabetes and that people with depression have a higher risk of developing type 2 diabetes. But until now, it wasn't clear if depression caused type 2, or vice versa, or if other factors were responsible for the link between the two conditions.    

In this latest study, researchers used a statistical method called Mendelian randomisation to analyse genetic and health information and determine whether type 2 diabetes and depression can cause the development of the other.    

The analysis revealed, for the first time, that depression directly causes an increased risk of developing type 2 diabetes, with higher body weight partly, but not wholly, explaining the effects of depression on type 2 diabetes. 

The researchers further pinpointed seven genetic variants that contribute to both type 2 diabetes and depression. The 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 the risk of type 2 diabetes.    

There was no evidence of a cause-and-effect relationship between type 2 diabetes and the development of depression. However, there are indirect links between the conditions, with both affected by common risk factors such as obesity and low levels of physical activity. The demands of living with the relentless day-to-day burden of type 2 diabetes can also be a factor in developing depression.    

 Dr Elizabeth Robertson, Director of Research at Diabetes UK, 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. 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."     

Dr Marika Kaakinen, last author on the paper from the University of Surrey, commented:  

"Our findings, while based on large genetic studies for hundreds of thousands of individuals and their health data, provide clues for the definition of an individual trajectories to diseases and risk of comorbidities. This research is important for everyone in the society." 

 There are now more than five million people in the UK living with diabetes, and about 90% of them have type 2 – which has many risk factors, including age, genetics, ethnicity and body weight. Depression and type 2 diabetes share some symptoms, such as being tired, sleeping a lot, and having difficulty concentrating. This can make it difficult to know whether symptoms are being caused by depression, diabetes, or both.   

For further information about diabetes and depression, including advice on how to get support if you need it, visit the Diabetes UK website at diabetes.org.uk. You can check your risk of type 2 diabetes by visiting riskscore.diabetes.org.uk.