Young adults with a history of depression have an increased risk of developing type 2 diabetes, according to a Canadian team.

"Our results are very important because the typical onset of depression occurs between 20 and 30 years of age," Dr. Jeffrey A. Johnson stated. "These are the people who are at highest risk of developing depression and, based on our study results, they seem to have the highest risk of developing type 2 diabetes."

Diabetes and depression often co-exist, and "depression is associated with worse outcomes in people with diabetes," Dr. Johnson and colleagues from the University of Alberta, Edmonton, write in the journal Diabetes Care.

It is not been entirely clear, however, whether people with a history of depression are somehow predisposed to developing diabetes, they explain.

The researchers used databases of Saskatchewan Health to identify 33,257 cases of type 2 diabetes among people at least 20 years of age, and each was matched to two nondiabetic "controls." The records were also used to any ascertain history of depression.

Patients with newly diagnosed diabetes were more likely to have a history of depression than were those without diabetes (4.9 percent vs. 3.8 percent, respectively).

This increased risk remained after taking into account various factors, "but was limited to subjects 20 to 50 years of age," the researchers report.

They note that there are several mechanisms that may be involved with this association. Depressed individuals are more likely to experience weight changes and less likely to partake in healthy behaviors such as exercise, both of which may increase the risk of diabetes.

Another possible explanation, according to the team, is that many of the medications used to treat depression cause weight gain and sedation, and may contribute to the development of diabetes.

SOURCE: Diabetes Care, May 2005.