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U.S. News & World Report The melancholy body
Mon
Dec 9,12:00 AM ET BY
MARIANNE SZEGEDY-MASZAK
An
elderly man came into the clinic at Duke University Medical Center looking
extremely depressed. Not surprising given what he had gone through during the
previous year. His wife had died, he had suffered a heart attack, and he was
taking a complicated cocktail of medications. But did his depression follow the
heart attack, or did an earlier but undiagnosed dark melancholy trigger his
cardiac problems? Increasingly,
it appears that what we call depression is not strictly psychological but is,
instead, a condition that occupies the whole body. "Depression is really
the only systemic disease that affects--and complicates--almost all other
diseases," says Philip Gold, the chief of clinical neuroendocrinology at
the National Institute of Mental Health. In fact, depression not only affects
and complicates existing disorders like diabetes, heart disease, cancer, even
osteoporosis; it might also trigger them. That
makes depression, already a huge public- health problem, even more serious. It
affects more than 18 million Americans; nearly 25 percent of all women and 10
percent of all men will be clinically depressed at some point in their lives.
The World Health Organization predicts that by 2020 depression will be second
only to heart disease as the leading cause of disability worldwide. The
heart. The
link to heart disease has been studied most extensively. Since a 1993 landmark
study, doctors have known that when patients are depressed and have a heart
attack or congestive heart failure, their outcomes tend to be poor compared with
people who are not depressed. "Depression appears to be an independent risk
factor for the development of heart disease," says Charles Nemeroff, chair
of psychiatry at Emory University School of Medicine. Of
course, someone who is depressed is less likely to exercise, eat right, and take
the correct medicines. But the connection goes much deeper, to the human stress
response gone awry. Under stress, the blood-clotting system, especially sticky
cells called platelets, goes on high alert to slow down bleeding should there be
a wound. However, both heart attacks and strokes are caused by the formation of
clots in arteries. One study found that depressed patients exhibited increased
platelet activation in comparison with normal subjects. Stress also activates
cytokines, chemical messengers from the immune system. Additionally, research
has pointed to elevated cytokine levels triggering inflammation in the heart. Other
researchers have examined the way that both depressed patients and cardiac
patients lose flexibility in their heart muscles. A normal heart moves easily
between its resting and beating states. But patients with severe coronary artery
disease or with depression have more rigid hearts, less able to respond to the
changing demands of the body for blood and oxygen. All
of this leaves researchers with a conundrum, put simply by Nancy Frasure-Smith,
a professor of psychiatry at McGill University who has studied depression in
cardiac patients for nearly 20 years: "Does depression cause cardiac
disease? Does cardiac disease cause depression? Or are they linked by a common
factor, but there is no causality? And the fact is, it can be all three." Diabetes.
In 1674, Thomas Willis wrote, "Diabetes is caused by melancholy." Now,
328 years later, it turns out he may have been on to something. There is a close
tie between depression and diabetes, says Sanford Garfield, the senior adviser
for biometry and behavioral research at the National Institute of Diabetes and
Digestive and Kidney Diseases. "Studies have shown that if you are
depressed you have twice the likelihood of being diabetic, and if you are
diabetic you have twice the likelihood of being depressed." And diabetes is
more likely to rage uncontrolled when it's accompanied by depression. While
there may be a number of reasons for this interrelatedness--and lifestyle cannot
be underestimated--one study has pointed to excess cortisol production. When
cortisol, also known as the "stress hormone," is secreted, it leads to
the release of amino acids. These acids are then turned into glucose for energy
for the brain. A depressed brain sends out signals that it needs more energy,
which can trigger cortisol production, thereby raising blood sugar. And that's a
great problem for diabetics. Another
study examined a brain region called the hippocampus and its role in the
regulation of glucose, as well as its need for glucose. Researchers concluded
that patients with Type I diabetes have a hippocampus that is damaged, even
atrophied, in a way that is true also for those with depression. One possible
explanation is that the brain-structure changes caused by diabetes can also
trigger depression. Another is that the brain-structure changes caused by
depression can exacerbate diabetes. Osteoporosis.
Depression
has also been studied in people with osteoporosis, a disease in which bone mass
disintegrates. Several studies have demonstrated that an earlier history of
depression was associated with marked osteoporosis. And another found a
significant association between reduced bone mineral density and depression. One
study, published last year in Trends in Endocrinology & Metabolism, concluded
that depression is a risk factor for osteoporosis as serious as smoking or a
family history of the disease. Why?
One hypothesis focuses on the interplay between cortisol, the stress hormone,
and interleukin 6, which is a cytokine and part of the immune system, in those
who are depressed and have osteoporosis. Frequently, depressed patients have
high levels of both, which may play a crucial role in bone loss. Cancer.
Who
wouldn't be depressed with a cancer diagnosis? Too often depression is seen as a
"normal reaction," which means, says Nemeroff, "that it doesn't
require any special treatment." The prevalence of depression among cancer
patients ranges from 23 percent to 60 percent. Obviously, the life-changing
nature of a cancer diagnosis has a great deal to do with this, but so do
cytokines. Cytokines--like
interleukin 6--are secreted by the immune system to fight anything that can harm
the body, like cancer or infections. Depression alters the immune system for
reasons that are not completely understood, but studies have shown that many
depressed patients have unusually high levels of cytokines. High levels can
provoke a syndrome called "sickness behavior"--a depressed mood,
sleeplessness, poor concentration. Once more, a chicken and egg conundrum
complicates the matter: Do cytokines released as cancer fighters trigger
depression, or do the cytokines triggered by the depression compromise the
immune response to the cancer? |