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A
Heavy Burden
In
a report published in the January 15, 1998, issue of the New England Journal
of Medicine, Bruce S. McEwen, a neuroscientist at Rockefeller University,
uses the term allostatic load to refer to the long-term physical effects
of the body's response to stress. Allostasis is derived from the Greek
word that means "to achieve stability through change." However, the price
our bodies pay for accommodating to stressful changes may be high; some
people develop a hyperactivity or hypoactivity of the normal stress response.
Too little production of stress hormones can be just as harmful as too
much, because it may trigger the secretion of other substances that compensate
for the loss. For example, if cortisol does not increase in response to
stress, inflammatory cytokines (signals), which are regulated by cortisol,
will rise.
On
the other hand, too much cortisol can predispose a person to infection,
bone loss, muscle weakening, and increased insulin production. Women with
a history of depression tend to have higher cortisol levels and lower
bone mineral density than those who are not depressed. And studies on
aging animals and humans suggest that chronic exposure to stress hormones
may accelerate changes in the brain that lead to memory loss.
No
one knows why stress hormones don't turn off in some people when the stressful
event has passed. It is also unclear why some individuals lose the ability
to produce stress hormones when they need them. The Rockefeller researchers
believe that regular, moderate exercise is probably the best way to counteract
the deleterious effects of stress. Physical activity can reduce insulin
levels raised by excessive cortisol secretion and also lowers blood pressure
and the heart's resting rate. People who exercise regularly may find that
they can more easily give up overeating or excessive alcohol consumption,
which they had previously used to quell stress.
The
Cancer Connection
There
is some, but less conclusive, evidence that stress may somehow be linked
to cancer. Over the past decade, studies have suggested that emotional
support not only enhances the lives of cancer patients but also prolongs
life. In a 1989 investigation, Stanford University researchers found that
women with metastatic breast cancer who participated in support groups
survived an average of 18 months longer than those who did not.
In
January 1998, a published report by Ohio State University researchers
indicated that breast cancer patients with high levels of anxiety about
their disease experienced a 20%-30% reduction in the effectiveness of
their natural killer (NK) cells compared to those with low levels of stress.
NK cells fight infection and cancer.
Previous
research has found that cancer patients who say they feel emotionally
supported have highly active NK cells; experts speculate that emotional
support boosts the activity of these white blood cells by decreasing stress.
However,
only a few studies have ever looked at whether reducing stress can actually
improve immune function and thus slow the progression of cancer. Now,
several such investigations are under way. One, by the same Ohio State
University researchers, is measuring baseline levels of NK activity and
other cellular reactions in 235 women with metastatic breast cancer who
will undergo surgery. After their operations, one group will attend support
groups for a year and learn ongoing coping skills; the other will not
attend such sessions. Stress levels, immune and endocrine response, and
cancer recurrence will be compared to the women's baseline measurements
after five years.
The
study will shed new light on the 1989 Stanford investigation, which was
designed only to examine the impact of particular kinds of emotional support
on quality of life; the investigators had not intended to look at survival
rates and did not measure immune responses or tumor growth.
However,
the same Stanford researchers are now in the process of replicating their
previous study, but this time they are monitoring cortisol levels, NK
cell activity, cancer recurrence, and survival rates. The final results
are expected to be published in about two years
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