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
For the study, published in the June 18 Journal of
the American Medical Association, diabetes
expert Sherita Hill Golden and her colleagues took
advantage of data generated by the Multi-Ethnic
Study of Atherosclerosis, which examined risk factors for
atherosclerosis, or hardening of the
arteries, in an ethnically diverse group of 6,814 men and
women 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
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
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 pre-diabetes 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 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.
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," Golden said.
"It's important that doctors be attuned to look for
both conditions in patients at risk for either
diabetes or depression," she added. "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 are Mariana Lazo, Hochang
Benjamin Lee and Constantine Lyketsos.
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.