"People usually think of these as two isolated conditions, but there is growing evidence that they are linked behaviorally and biologically,” says study researcher Frank Hu, MD, PhD, MPH, professor of nutrition and epidemiology at the Harvard School of Public Health in Boston. “This data provide strong evidence that we should not consider these two isolated conditions any longer.”
About 23.5 million Americans have diabetes, and about 14.8 million Americans have major depressive disorder in a given year, according to statistics in the new report.
Depression and Diabetes Risk
Depression increased the risk for diabetes, and diabetes increased the risk for depression, the study shows. Specifically, women who were depressed were 17% more likely to develop diabetes even after the researchers adjusted for other risk factors such as weight and lack of regular exercise.
Those women who were taking antidepressants were 25% more likely to develop diabetes than their counterparts who were not depressed, the study shows.
Women with diabetes were 29% more likely to develop depression after taking into account other depression risk factors, and those women who took insulin for their diabetes were 53% more likely to develop depression during the 10-year study.
While certain factors such as physical activity and body mass index may partially explain the link between depression and diabetes, they do not completely explain the connection, Hu tells WebMD.
The common denominator may be stress, Hu says.
People who are depressed have elevated levels of stress hormones such as cortisol, which can lead to problems with glucose or blood sugar metabolism, increased insulin resistance, and the accumulation of belly fat -- all diabetes risk factors, he says.
But “there is long-term stress and strain associated with diabetes management such as blood sugar control and treatment for complications, and this can lead to decreased quality of life and increased probability of depression,” he says.
“Both are very common diseases,” says Leonid Poretsky, MD, director of the Friedman Diabetes Institute at Beth Israel Medical Center in New York City. “Diabetes can make depression worse because diabetes is chronic illness with a lot of worries.”
“So much of the treatment for diabetes is self-care, and people who are depressed may not take good care of themselves,” he says. “They don't exercise as much and may have other issues in terms of watching their diet, checking their blood sugar, and taking medications.”
Certain medications used to treat depression can also increase risk for developing diabetes, he says.
“It can be a vicious cycle. Both diseases have to be addressed at the same time,” Poretsky says. “If control of diabetes is deteriorating, look for depression as a possible cause of this deterioration.”
“This study is interesting, and one of a number of studies that points to a bi-directional link between diabetes and depression,” says Jeffrey Gonzalez, PhD, assistant professor of medicine and epidemiology and population health at Albert Einstein College of Medicine in the Bronx, N.Y. “The emotional side of diabetes is an important one to attend to in the treatments of this illness.”
“This speaks to the burden associated with diabetes,” Gonzalez says. “Changes in diet and lifestyle, having to take injections can lead to increased levels of distress.”
Doctors need to do a better job of addressing the emotional side of diabetes, he says. “We know that if you are distressed once you do have diabetes, you are at increased risk for poor self-management, complications, and death.”