People with diabetes are much more prone to depression and stress than other individuals, and these mental health problems in diabetics are tied to an increased risk of strokes and deaths from cardiovascular disease, a U.S. study suggests.

The worst outcomes may result when people with diabetes suffer from both stress and depression at the same time, the study found. This trifecta of health problems was linked to more than double the risk of death from heart disease faced by people without any of these medical issues.

"Our study is one of the first to show a pattern of increased likelihood of adverse cardiovascular outcomes in those with diabetes compared to those without diabetes - first with increased likelihood for either (stress or depression) alone, and then an even higher likelihood when both behavioral co-morbidities were reported," lead study author Doyle Cummings of East Carolina University Brody School of Medicine, said by email.

To assess the impact of these mental health problems on heart disease and stroke risk, Cummings and colleagues reviewed data on nearly 22,000 adults including close to 4,100 with diabetes.

People in the study were 64 years old on average, 58 percent of them were female, 42 percent were black, and 56 percent lived in the southeastern U.S. region known as the "Stroke Belt" for its high prevalence of these cardiovascular events.

At the start of the study, roughly 19 percent of participants had diabetes, while 10 percent reported increased depressive symptoms and 28 percent reported elevated stress.

Among subjects with diabetes, those reporting heightened stress or depression - or both - were more likely to be women, black, poor, and live in the Stroke Belt.

For people with diabetes, having either stress or depression increased their risk of death from cardiovascular disease by 53 percent, compared with diabetics without these mental health problems. Diabetics with both stress and depression had more than double the death risk.

For those without diabetes in the study, there was a trend toward a greater risk of death from cardiovascular disease when they had stress or depression but the difference between people with and without these problems wasn't big enough to rule out the possibility that it was due to chance.

The study wasn't designed to prove that stress or depression cause strokes or death from cardiovascular disease.

Other limitations of the study include a lack of data on how long people had diabetes, which can influence cardiovascular risk, and the potential that certain factors not measured in the study might have influenced deaths, the authors concede in Diabetes Care.

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Even so, the findings point to the need for more clinicians to screen for depression and stress in primary care settings, where most people with diabetes receive care, Cummings said.

"In our culture, it's easy to be sidetracked by all the other things that we commonly think about checking when someone has diabetes, such as monitoring their blood sugars daily and taking medications, and watching for things like high blood pressure, foot sores, cholesterol, and kidney problems," said Dr. Erik Vanderlip of the University of Oklahoma School of Community Medicine.

"We often forget to think about depression and stress as independently contributing to heart disease through mechanisms which we haven't yet fully figured out," Vanderlip, who wasn't involved in the study, said by email. "So we rarely screen for it, or diagnose it, despite having treatments that can change it over time."