MONDAY, Nov. 22 (HealthDay News) -- Diabetes and depression are
conditions that can fuel each other, a new study shows.
The research, conducted at Harvard University, found that study
subjects who were depressed had a much higher risk of developing
diabetes, and those with diabetes had a significantly higher risk
of depression, compared to healthy study participants.
"This study indicates that these two conditions can influence each other and thus become a vicious cycle," said study co-author Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health in Boston. "Thus, primary prevention of diabetes is important for prevention of depression, and vice versa."
In the United States, about 10 percent of the population has
diabetes and 6.7 percent of people over the age of 18 experience
clinical depression every year, according to the researchers.
Symptoms of clinical depression include anxiety, feelings of
hopelessness or guilt, sleeping or eating too much or too little,
and loss of interest in life, people and activities.
Diabetes is characterized by high blood sugar and an inability
to produce insulin. Symptoms include frequent urination, unusual
thirst, blurred vision and numbness in the hands or feet.
About 95 percent of diabetes diagnoses are type 2, and often are
precipitated by obesity.
The researchers found that the two can go hand in hand.
The study followed 55,000 female nurses for 10 years, gathering
the data through questionnaires. Among the more than 7,400 nurses
who became depressed, there was a 17 percent greater risk of
developing diabetes. Those who were taking antidepressant medicines
were at a 25 percent increased risk.
On the other hand, the more than 2,800 participants who
developed diabetes were 29 percent more likely to become depressed,
with those taking medications having an even higher risk that
increased as treatment became more aggressive.
Tony Z. Tang, adjunct professor in the department of psychology
at Northwestern University, said that participants who were taking
medications for their conditions fared worse because their
illnesses were more severe.
"None of these treatments are cures, unlike antibiotics for infections. So, depressed patients on antidepressants and diabetic patients on insulin still frequently suffer from their main symptoms," said Tang. "These patients fare worse in the long run because they were much worse than the other patients to start with."
Tang cautioned against drawing too many conclusions from the
study. He noted that the correlations between diabetes and
depression declined markedly when excessive weight and inactivity
were controlled for in the study.
"This suggests that much of the observed correlation between depression and diabetes comes from confounding variables," he said. "In layman's terms, being fat and having an unhealthy lifestyle makes people more likely to be depressed, and [also] more likely to have diabetes."
But if research establishes a strong connection between the two
illnesses it could advance treatment, Tang added.
"If a substantial causal connection is established between the two disorders, it would be rather novel and it could potentially change how we understand and treat both disorders," Tang said.
Dr. Joel Zonszein, director of the Clinical Diabetes Center at
Montefiore Medical Center in New York City, said establishing
causal relationships is difficult in a study based on
questionnaires because self-reports can be inaccurate.
"This is not ideal," he said. "It's difficult to say what is causing what, if one is causing the other. This is very difficult to elucidate."
A large, controlled, randomized study is needed, said Zonszein,
who is also a professor of clinical medicine at Albert Einstein
College of Medicine, in New York City.
But he praised the research, noting that tracking such as large
number of subjects "over a long period of time" strengthened the
Hu, also a professor of medicine at Harvard University, said the
study conclusions were valid. When two conditions share the same
risk factors (obesity and lack of exercise), "we can still say that
the conditions are linked and one is both the cause and consequence
of the other condition," he explained.
Depression can affect blood sugar levels and insulin metabolism
through increased cortisol, contributing to unhealthy eating
habits, weight gain and diabetes, he said.
"On the other hand, management of diabetes can cause chronic stress and strain, which in the long run, may increase risk of depression," said Hu. The two "are linked not only behaviorally, but biologically."
For more on diabetes, go to
U.S. National Library of Medicine.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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