Diabetes and depression have long been linked. About 12% of those with diabetes have major depression, and about 10 to 20% have minor depression.
What experts have long debated, however, is whether reducing the depression can also help control diabetes.
Now, in a new analysis, German researchers have found that reducing depressive symptoms does indeed translate to better blood glucose control, even increasing the chances of getting to the goal of a hemoglobin A1C under 7.5.1
There could be many explanations for why reducing depression helps blood sugar, says study investigator Andreas Schmitt, PhD, a postdoctoral researcher at the Research Institute of the Diabetes Academy Mergentheim in Germany. It could be that the less depressed people are, the better care they take of themselves. And the more depressed, the worse care. "Evidence suggests a behavioral relationship between depression and glycemic control, mediated by impaired diabetes self-management," he tells EndocrineWeb.
"Depression is associated with reduced motivation, reduced activity, suboptimal lifestyle factors such as an unhealthy diet and smoking," he says. "Adherence to diabetes treatment regimen may be reduced."
The link could go the other way, too, he says, with poor diabetes control perhaps triggering depression or worsening it.
Depression is often stressful, of course. Dr. Schmitt says that "under chronic stress conditions, blood glucose levels may vary more strongly and poorer glycemic control can result." Chronic, low-grade inflammation is linked with both stress and depression, and that could explain the poorer control. "There is evidence supporting that inflammation can lead to hyperglycemia and anti-inflammatory medication might improve glycemic control," he adds.
The researchers followed 181 men and women, on average age 45, with type 1 and type 2 diabetes. They were on a variety of diabetes medicines, but most were on insulin therapies, as type 1 affected 63% of the people in the study.
At the start, the majority, 76%, had A1Cs of 7.5 or higher.
They each took a standard depression test, called the CES-D, with questions such as whether they are bothered by everyday events, if their appetite lagged, if they had trouble concentrating or sleeping, and their mood.2
The possible scores range from zero to 60, and these men and women averaged a score of 23 at the start. "Depression levels included both major depression as well as elevated depressive symptoms,'' the latter is known as subclinical depression, Dr. Schmitt says.
At the end of the study, the average decline in the depression scores was 5 points, down to 18. And nearly half showed scores of 15 or lower, suggesting a recovery.
The A1C dropped from an average of 8.8 at the study start to 8.1 after a year. And 35% of the people got to the target of under 7.5.
Next, the researchers looked to see if the lower depression scores predicted lower A1C, and found they did. Each one-point reduction in depression score raised the odds of reaching the A1C target by 4%. Those whose score dropped enough to be termed recovered were twice as likely to reach that A1C goal.1
The new analysis was a secondary evaluation of the researchers' previous study, called DIAMOS (Diabetes-Specific Cognitive Behavior Treatment Program). In this original study, the same researchers compared cognitive behavioral therapy, commonly called talk therapy, with simply getting care for diabetes. The researchers looked to see how much the depressive symptoms declined and also if the A1C declined.
After 12 months, those getting talk therapy showed reductions in depression, but so did the comparison group. Initially, the results seemed to speak out against the benefit of treating the depression, so the researchers decided to look at the results in a different way, conducting the secondary analysis. They looked at whether the reduction in depression could predict improved blood sugar control, regardless of whether the people got conventional depression treatment or not. And that's when they found that it did. When the depression went down, so did the blood glucose.
The study is published in the Journal of Diabetes and Its Complications.1
"This study is consistent with our expectations," says Elena Christofides, MD, FACE, CEO of Endocrine Associates in Columbus, Ohio, and a member of the EndocrineWeb editorial board.
In the original study, she notes, both the group getting ''talk therapy'' and the group getting regular diabetes care had their depression lessen, and she speculates as to why that was so. "It's the interaction," she says.
Both groups had interaction and care from health care providers, she says, and ''a simple human connection is enough to make people feel better. When you feel better, you take better care of yourself."
Whichever the intervention—standard care or talk therapy—those who responded to the intervention in a positive way reduced their depression, Dr. Christofides says.
If interactions with health providers aren't enough to improve depression, what to do? That decision must be individualized, as Dr. Schmitt says.
"Not all patients respond to antidepressant medication," he says. He adds that ''cognitive behavioral therapies addressing both depressive cognition and behavior change regarding diabetes'' are most likely to help the diabetes control.