Study sees major depression connection to diabetes

Elderly people who are depressed are more likely to become diabetic than those who are not, according to a study that suggests depression may play a role in causing the most common form of diabetes.

Writing on Monday in the Archives of Internal Medicine, the researchers said people with a high number of symptoms of depression were about 60 percent more likely to develop type 2 diabetes, formerly called adult-onset diabetes, than people not considered depressed.
Unlike some other studies examining a link between depression and diabetes, this one looked at the effects not only of single bouts of depression but also of chronic depression and depression that worsened over time. It found an increased risk for diabetes in each of those scenarios.

Researchers tracked 4,681 men and women in North Carolina, California, Maryland and Pennsylvania ages 65 and older, with an average age of 73, who did not have diabetes when the study began in 1989.

For 10 years, they were screened annually for 10 symptoms of depression, including those related to mood, irritability, calorie intake, concentration and sleep.

"People who report higher depressive symptoms may not take as good a care of themselves as they should," lead researcher Mercedes Carnethon of the Northwestern University's Feinberg School of Medicine said in an interview.

"For example, they may be less physically active, and thus more likely to gain weight, which is the primary risk factor for diabetes," Carnethon said.

But the study statistically accounted for known lifestyle risk factors for diabetes like being overweight and sedentary, and still found that depression increased the risk of diabetes.

Carnethon said the findings suggest depression may play a role in causing diabetes. While the study did not explore possible biological mechanisms, Carnethon said a high level of the stress hormone cortisol in depressed people may be the reason.

Diabetes is marked by high levels of blood glucose resulting from defects in the production or action of insulin, which allows glucose to enter the body's cells for use as fuel. High cortisol levels, the researchers said, may cut insulin sensitivity and raise fat deposits around the waist.

"Diabetes not only causes heart disease, but is strongly related to strokes, blindness, kidney failure, amputations. Diabetes is a very serious condition that's highly prevalent in older adults," Carnethon said.

Diabetes is a growing worldwide problem, closely tied to obesity. Type 2 diabetes accounts for about 95 percent of all cases.

The findings point to the importance of doctors screening older adults for depression and, if it's present, for diabetes risk, Carnethon said.