In a new study published in Archives of General Psychiatry, researchers followed 19,000 California residents with diabetes between ages 30 and 75 for 3 to 5 years. About a fifth of the participants had depression too.
Two percent of those with diabetes and depression developed dementia or Alzheimer's during the study, while only one percent of those with diabetes but no depression developed dementia or Alzheimer's.
While this may sound like dreary news, don't get too despondent. Lead author Wayne Katon, a professor of psychiatry and behavioral sciences at the University of Washington's School of Public Health, told U.S. News that since depression is treatable, patients and doctors might be able to lower dementia risk too.
"So the important thing to focus on here is that there are very effective treatments for depression," said Katon. "And so if you're a diabetic who does have depression it's very important to get it attended to. Just as important as getting your diabetes itself treated."
Luckily, some of the things you can do to boost your mood -- eating a healthy diet, exercising, and quitting smoking -- can also cut your risk of diabetes. So while the three D's definitely seem to be linked, that's only a bad thing if you don't do anything about them.