Two common conditions — depression and diabetes — frequently appear together, and a new study by researchers from the Harvard School of Public Health suggests that each illness may be both a consequence and a contributor to the other.
The 10-year study followed 65,381 women, ages 50 to 75, who were participating in the Nurses’ Health Study. Over the course of the research, depression and new cases of Type 2 diabetes were monitored: 2,844 women from the group were diagnosed with diabetes and 7,415 women developed depression — unsurprising numbers based on the prevalence of both illnesses.
Researchers also found a correlation between the conditions: women who suffered from depression were 17% more likely to develop Type 2 diabetes during the study period than women who weren’t depressed; women with diabetes were 29% more likely to develop depression than women without diabetes, even after adjusting for other mood disorders and risk factors, such as weight and lack of frequent exercise.
Additionally, the more severe the depression or diabetes was, the more likely that women would develop the other disease. Women whose diabetes was serious enough to require insulin, for instance, were 53% more likely to develop depression during the 10-year time frame, compared with women without diabetes. And women who took antidepressants to manage their depression were 25% more likely than undepressed women to develop diabetes.
Lead researcher Dr. Frank Hu, professor of nutrition and epidemiology, told WebMD that factors such as physical activity and body mass index (BMI) might partially explain the connection between the two illnesses, but that the more likely common denominator is stress.
High levels of stress hormones, which are often found in people who are depressed, can lead to problems with glucose and blood sugar metabolism, increased insulin resistance and an accumulation of stomach fat — all risk factors for diabetes. Depression also tends to lead to unhealthy lifestyle behaviors, such as eating a poor diet and not exercising, which may further up the risk of diabetes.
Conversely, people with diabetes must deal with managing a chronic disease, which requires changing diet and lifestyle and adjusting to various prescription medications, so it’s easy to see how the disease could increase stress levels and risk of depression.
The study’s authors say, therefore, that doctors should take care to address the psychological aspects of disease management with diabetes patients, and pay attention to blood sugar levels and other signs of diabetes in patients diagnosed with clinical depression.
The new study was published this week in the Archives of Internal Medicine.