Study findings show that there is a link between the use of antidepressant drugs and diabetes, investigators here at the 66th Scientific Sessions of the American Diabetes Association announced. This is the first report of such an association, they say.

Depression is two- to three-times higher in diabetics than in the general population. In addition, 10 percent to 15 percent of the U.S. population takes antidepressants, “and the numbers are increasing,” Dr. Richard R. Rubin of The Johns Hopkins University School of Medicine in Baltimore, Maryland, told meeting attendees Saturday.

Dr. Rubin, a co-investigator with the Diabetes Prevention Program Research Group, presented findings for 3,187 trial participants with elevated blood glucose values, indicating that they were pre-diabetic. Of these subjects, 5.7 percent reported regular use of antidepressants at the beginning of the study. Elevated scores on the Beck Depression Inventory, a common test used to diagnose depression, were found for 10.3 percent.

Patients were randomly assigned to one of three subgroups: metformin therapy, intended to prevent the onset of diabetes; intensive lifestyle modification; or placebo. The average length of patient follow-up was 3.2 years.

High scores on the Beck Depression Inventory alone did not predict the development of diabetes. However, after the influence of weight, and metabolic and demographic factors of the subjects at the beginning of the study was factored in, the investigators found that antidepressant use did predict diabetes. Patients in the placebo group had almost twice the risk of developing diabetes and those in the intensive lifestyle modification arm had almost three-times the risk. No increased risk of diabetes was associated with depression in patients in the metformin subjects.

“We don’t have a clue” as to why the association exists, Dr. Rubin told Reuters Health. In their abstract, the investigators note that the mechanism “does not appear to be increased weight or fasting plasma glucose or insulin levels.”

Metformin acts primarily in the liver, and may change the body’s response to antidepressants. “Or, the drug could be a marker for something else,” Dr. Rubin suggested.

If the findings are confirmed in further studies, “it would have enormous public health implications,” he commented. “In the meantime, patients should not stop taking their antidepressants. They have been proven to have tremendous relief, but those at risk of diabetes should have their blood sugar monitored frequently and perhaps - perhaps - begin oral anti-diabetic treatment early.”

Dr. Rubin emphasized that patients in this study were all at very high-risk for developing diabetes.