The study included just over 4,100 people with diabetes. Nearly 500 of these people met the criteria for having major depression during the five-year study period.
The average age of the study volunteers was 63, and the average duration of diabetes was 10 years. Most -- 96 percent -- had type 2 diabetes. About one-third were taking insulin to control their diabetes. Just 1.4 percent were experiencing complications of diabetes.
In the five years before the study began, 8 percent of those with both depression and diabetes reported having had a severe hypoglycemic episode compared to 3 percent of the non-depressed people with diabetes. During the five-year study, nearly 11 percent of the depressed people with diabetes had a severe hypoglycemic episode compared to just over 6 percent of the non-depressed people with diabetes.
The risk of hypoglycemia was unaffected by the type of treatment received. People taking oral medications were just as likely to have a hypoglycemic episode as those taking insulin, according to the study.
Overall, people with diabetes who were depressed had a 42 percent greater risk of having a severe hypoglycemic episode, and a 34 percent higher risk of having a greater number of hypoglycemic episodes.
Katon said there are two likely explanations for these increased risks. One is that depression leads to psychobiological changes that cause big fluctuations in blood sugar levels, which may make it harder to prevent low blood sugar levels.
The other possibility is that depression leads to a lack of interest in the self-care that's necessary to manage diabetes well. "People who are depressed may be less likely to test their blood sugar levels regularly. They may adhere to their medications less well. They may forget if they've taken them, and then end up taking an additional dose," said Katon.
Another expert, Eliot LeBow, a
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