Depression and Diabetes: Fellow Travelers, Researchers Say

Researchers have long known that type-2 diabetes and depression often
go hand in hand. However, it's been unclear which condition develops
first in patients who end up with both. Now, a new study led by Johns
Hopkins doctors suggests that this chicken-and-egg problem has a dual
answer: Patients with depression have an increased risk of developing
type-2 diabetes, and patients with type-2 diabetes have an increased
risk of developing depression.

For the study, published in the June 18 Journal of the American
Medical Association, diabetes expert Sherita Hill Golden, M.D.,
M.H.S., and her colleagues took advantage of 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. Participants in the MESA study identified themselves when they
enrolled as white, black, Hispanic or Chinese.

During MESA, participants 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 study also collected information on other atherosclerosis risk
factors, such as 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.

Mining the data for their own purposes, Golden and her colleagues
excluded from their analysis all participants who had high fasting
glucose, an indication of diabetes, at the initial clinic visit. They
then looked to see whether participants who initially had elevated
symptoms of depression, as indicated through a questionnaire, were
more likely than those who didn't to develop high fasting glucose at
the end of the three-year study period.

Results showed that those with elevated depressive symptoms were 42
percent more likely overall to develop diabetes by the end of the
study than those without these symptoms. Moreover, the stronger the
symptoms, the higher the risk of diabetes, a "dose response" that
lends strength to the findings.

Even when the researchers accounted for such factors as overweight,
lack of exercise, and smoking, the risk of developing diabetes was
still 34 percent higher for patients with depressive symptoms.

To investigate whether diabetes could lead to depression, Golden and
her colleagues used the same pool of MESA information and excluded
those who had elevated depressive symptoms at the initial clinic
visit. Then, they looked to see whether those who had high fasting
glucose-with or without a formal diagnosis of diabetes-were more
likely to develop depressive symptoms by the end of the study.

The researchers found that patients treated for diabetes, about 9
percent of the group, were about 54 percent more likely to develop
elevated depressive symptoms than those without diabetes.

Surprisingly, those with prediabetes or untreated diabetes were about
25 percent less likely to develop elevated depressive symptoms than
people with normal fasting glucose, a finding Golden's team cannot
explain at this time.

Golden, an associate professor of medicine and epidemiology at the
Johns Hopkins University School of Medicine, speculates that
depression may lead patients to develop behaviors that trigger
diabetes or make it worse, such as overeating, not exercising or
smoking. Similarly, keeping up with the often extensive treatment
regimens to care for their diabetes may make patients' depression
worse. Understanding how one condition might lead to another could
improve treatments for both problems, she says.

"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," says Golden. "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.

"It's important that doctors be attuned to look for both conditions
in patients at risk for either diabetes or depression," Golden adds.
"We may want to develop interventions for both treatments, instead of
just one or the other."

Other Johns Hopkins researchers who participated in this study
include Mariana Lazo, M.D.. M.Sc.; Hochang Benjamin Lee, M.D.; and
Constantine Lyketsos, M.D., M.H.S.

The MESA study was supported by grants from the National Heart, Lung,
and Blood Institute. Golden and her colleagues' research was
supported by a Patient-Oriented Mentored Scientist Award through the
National Institute of Diabetes and Digestive and Kidney Diseases.