Diabetes may appear to have nothing to do with mental disorders, but new research suggests otherwise. Your risk of type 2 diabetes may be higher if you have been diagnosed with a mental illness.
The study shows that the disease is more common among people with any psychiatric disorder, especially those with sleep disorders, binge eating disorders, and substance use disorders.
Rates were also higher in people with depression, anxiety disorders, as well as psychotic disorders including schizophrenia.
"From previous research, we know that people with a psychiatric disorder live significantly shorter than people without a psychiatric disorder," Nanna Lindekilde, PhD candidate at the University of Southern Denmark and study author, told Verywell via email. "One of the mechanisms that explains this might be the development of type 2 diabetes, and suboptimal detection and treatment."
The study was published in Diabetologia, the journal of the European Association for the Study of Diabetes (EASD), in late November.
Type 2 diabetes develops when cells don’t respond normally to insulin—a hormone that lets blood sugar into the cells for use as energy. When too much sugar goes unprocessed, high blood sugar damages the body and can lead to other serious health problems such as heart disease, vision loss, and kidney disease. Changes in insulin response are often caused by lifestyle factors like an unbalanced diet.
Between 6% to 9% of the global population has been diagnosed with type 2 diabetes. In the U.S., that rate is slightly higher at 1 in 10. Rates have been rising since 1990, and are expected to continue.
At the same time, about 1 in 5 people around the world are dealing with a common mental condition, such as anxiety, substance use, and mood-related disorders, at any given time.
To investigate the ties between these common conditions, Lindekilde and colleagues analyzed 32 systematic reviews based on 245 original studies. The studies looked at the prevalence of type 2 diabetes among populations with a psychiatric diagnosis.
Trends showed that overall, people with a sleep disorder had the highest rates of type 2 diabetes (40%), followed by:
A simple blood test will let you know if you have diabetes. You can get your blood sugar tested at a health fair or pharmacy, and follow up at a clinic or doctor’s office to make sure the results are accurate.
Understanding the link between type 2 diabetes and mental conditions requires further research, but Lindekilde said there are some theories.
For example, it could be just a buildup of factors. Harmful behaviors—such as unbalanced diet, smoking, physical inactivity, and poor sleep quality—combined with genetics and use of psychotropic medication, may explain why type 2 diabetes is more prevalent in individuals with a psychiatric disorder.
For sleep disorders, specifically, the connection is clearer.
"We know that there is a bidirectional association between sleep problems and type 2 diabetes," Lindekilde said. That is, people with diabetes often experience sleep problems in part due to the increased need to urinate in the middle of the night.
However, Lindekilde added, people with sleeping problems more often develop type 2 diabetes in general.
"It may be the case that poor sleep quality leads to snacking behaviors during the day, in an attempt by the individual to regain energy, and to lower levels of physical activity due to fatigue," she said.
Type 2 diabetes is a growing global public health concern, as are mental health conditions. Understanding how these two intertwine will be important in helping people with either or both conditions. In some cases, type 2 diabetes can be reversible.
Lindekilde said that more research is needed to not only understand the high prevalence of type 2 diabetes in people with a psychiatric disorder but also to raise awareness about that increased risk.
"There is a need for prevention initiatives that help to prevent not only diabetes but also cardiovascular diseases through healthier lifestyles in people with a psychiatric disorder," she said.
From previous research, Lindekilde and colleagues know that early detection and subsequent early treatment are important to minimize and delay the complications of type 2 diabetes.
Currently, Lindekilde is collaborating on an ongoing study with more than 250,000 Danish individuals that investigates factors that may explain the link between diabetes and mental health conditions. "We need to learn more regarding which mediating mechanisms play the biggest role, and to explore whether the mechanisms differ across the different categories of psychiatric disorders," she said.
Previous research shows that people with serious mental illness live significantly shorter than the general population.
Experts suspect that this means that having a mental health disorder can lead to healthcare disparities. They may be more vulnerable to health problems due to social and lifestyle factors yet receive less attention and experience more gaps in routine health care.
For example, Lindekilde added, people with schizophrenia live 15 years shorter on average. "One of the mechanisms that might explain this could be the development of type 2 diabetes without optimal detection or treatment," Lindekilde said.
"Our findings again highlight the importance of focusing on type 2 diabetes risk and treatment in individuals with a psychiatric disorder," she said.