Depression and Type 2 diabetes have a lot in common. Both disorders are strongly influenced by lifestyle factors such as sleep and diet, and both are associated with higher rates of inflammation and mortality. Each disorder is also a risk factor for the other.
“Having depression increases the risk of developing diabetes, and having diabetes increases the risk for developing depression,” Dolores Malaspina, MD, a psychiatrist and epidemiologist at New York University School of Medicine, told Psychiatry Advisor. A study published earlier this year in the International Journal of Endocrinology, which was co-authored by Malaspina, is one of many showing a connection between the two diseases.1
The researchers analyzed the data of 14,373 subjects from the National Health and Nutrition Examination Survey (NHANES), each of whom completed a Patient Health Questionnaire-9 (PHQ-9) depression screening and had their glucose functioning assessed via the hemoglobin A1C (HbA1c) test. According to the results, approximately 38% of participants with major depressive disorder had elevated HbA1c levels, of which many of them were unaware. Conversely, it has been estimated that depression affects 20% of people with diabetes,2 and the combination leads to poorer diabetes management and elevated mortality rates. Research published in PLOS ONE in 2013 found that, in people with diabetes, depression is associated with 50% increased risk of mortality.2
“Many of the symptoms and behaviors observed in depression are known to be risk factors for diabetes, including poor sleep, changes in weight, carbohydrate craving and less physical activity,” says Malaspina, who is also the Anita and Joseph Steckler Professor of Psychiatry and Child Psychiatry at NYU Langone Medical Center. Additionally, depression is linked with increased levels of cortisol, a stress hormone that counteracts the action of insulin, thereby causing insulin resistance and diabetes.
On the other hand, “the insulin resistance and hyperglycemia of diabetes can directly impair the mechanisms of brain plasticity and produce depression though a neurotoxic process,” and the stress of coping with a chronic disease like diabetes is known to increase the risk of depression. The two disorders may also share common genetic and environmental components, as both “involve inflammation and are more common in people who experienced prenatal adversity or early life trauma and have severe ongoing stressors,” said Malaspina.