Washington, June 18 : Johns Hopkins doctors say that a study conducted by them shows that people with depression have an increased risk of developing type-2 diabetes, and vice versa.
Dr. Sherita Hill Golden and her colleagues used the data generated by the Multi-Ethnic Study of Atherosclerosis (MESA) - which examined risk factors for atherosclerosis, or hardening of the arteries, in an ethnically diverse group of 6,814 men and women between ages 45 to 84 - for their study.
Participants in the MESA study - who identified themselves as white, black, Hispanic or Chinese at the time of their enrolment - made three visits to clinics over the course of three years to be examined for various atherosclerosis risk factors, including type-2 diabetes and symptoms of depression, which could serve as a precursor for full-blown clinical depression.
The researchers behind that study also gather information on other atherosclerosis risk factors - like participants' body-mass indices, blood pressure, diet and exercise patterns, and smoking habits, as well as information correlated with health in general, such as income and socioeconomic factors.
When Golden and her colleagues used the data for their study, they excluded from their analysis all participants who had high fasting glucose, an indication of diabetes, at the initial clinic visit.
The researchers later investigated whether the subjects who initially had elevated symptoms of depression, as indicated through a questionnaire, were more likely than those who did not to develop high fasting glucose at the end of the three-year study period.
They observed that the subjects with elevated depression symptoms were 42 per cent more likely overall to develop diabetes by the end of the study than the participants without such symptoms.
What lends strength to the findings was the fact that the subjects' likelihood of developing diabetes increased as the symptoms grew stronger.
The risk of developing diabetes was still 34 per cent higher for patients with depressive symptoms even when the researchers accounted for such factors as overweight, lack of exercise, and smoking.
With a view to seeing whether diabetes could lead to depression, Golden's team excluded from their analysis all subjects who had elevated depressive symptoms at the initial clinic visit.
The researchers then went on to investigate whether people having high fasting glucose - with or without a formal diagnosis of diabetes - were more likely to develop depressive symptoms by the end of the study.
It was observed that patients treated for diabetes, about nine per cent of the group, were about 54 per cent more likely to develop elevated depressive symptoms than those without diabetes.
Golden and her colleagues were surprised to see that people with prediabetes or untreated diabetes were about 25 per cent less likely to develop elevated depressive symptoms than people with normal fasting glucose, a finding they cannot explain at the moment.
The researchers speculate that depression may cause patients to develop behaviours that trigger diabetes or make it worse - such as overeating, not exercising or smoking.
They also believe that keeping up with the extensive treatment regimens to care for their diabetes might worsen patient's depression.
Golden insists that gaining a deeper understanding of how one condition might lead to another may helpfully improve treatments for both problems.
"Having both diabetes and depression can make it difficult for patients to get the good clinical outcomes that we like to see for each of these conditions. To make sure that patients with diabetes and depression receive the best care, we wanted to get to the bottom of the connection between these two conditions," she says.
"It's important that doctors be attuned to look for both conditions in patients at risk for either diabetes or depression. We may want to develop interventions for both treatments, instead of just one or the other," she adds.
The study has been published in the Journal of the American Medical Association.