Stress wreaks havoc on the mind and body. For example, psychological
stress is associated with greater risk for depression, heart disease and
infectious diseases. But, until now, it has not been clear exactly how
stress influences disease and health.
A research team led by Carnegie Mellon University's Sheldon Cohen has
found that chronic psychological stress is associated with the body
losing its ability to regulate the inflammatory response. Published in
the Proceedings of the National Academy of Sciences, the research shows
for the first time that the effects of psychological stress on the
body's ability to regulate inflammation can promote the development and
progression of disease.
"Inflammation is partly regulated by the hormone cortisol and when
cortisol is not allowed to serve this function, inflammation can get out
of control," said Cohen, the Robert E. Doherty Professor of Psychology
within CMU's Dietrich College of Humanities and Social Sciences.
Cohen argued that prolonged stress alters the effectiveness of
cortisol to regulate the inflammatory response because it decreases
tissue sensitivity to the hormone. Specifically, immune cells become
insensitive to cortisol's regulatory effect. In turn, runaway
inflammation is thought to promote the development and progression of
many diseases.
Cohen, whose groundbreaking early work showed that people suffering
from psychological stress are more susceptible to developing common
colds, used the common cold as the model for testing his theory. With
the common cold, symptoms are not caused by the virus -- they are
instead a "side effect" of the inflammatory response that is triggered
as part of the body's effort to fight infection. The greater the body's
inflammatory response to the virus, the greater is the likelihood of
experiencing the symptoms of a cold.
In Cohen's first study, after completing an intensive stress
interview, 276 healthy adults were exposed to a virus that causes the
common cold and monitored in quarantine for five days for signs of
infection and illness. Here, Cohen found that experiencing a prolonged
stressful event was associated with the inability of immune cells to
respond to hormonal signals that normally regulate inflammation. In
turn, those with the inability to regulate the inflammatory response
were more likely to develop colds when exposed to the virus.
In the second study, 79 healthy participants were assessed for their
ability to regulate the inflammatory response and then exposed to a cold
virus and monitored for the production of pro-inflammatory cytokines,
the chemical messengers that trigger inflammation. He found that those
who were less able to regulate the inflammatory response as assessed
before being exposed to the virus produced more of these
inflammation-inducing chemical messengers when they were infected.
"The immune system's ability to regulate inflammation predicts who
will develop a cold, but more importantly it provides an explanation of
how stress can promote disease," Cohen said. "When under stress, cells
of the immune system are unable to respond to hormonal control, and
consequently, produce levels of inflammation that promote disease.
Because inflammation plays a role in many diseases such as
cardiovascular, asthma and autoimmune disorders, this model suggests why
stress impacts them as well."
He added, "Knowing this is important for identifying which diseases
may be influenced by stress and for preventing disease in chronically
stressed people."
In addition to Cohen, the research team included CMU's Denise
Janicki-Deverts, research psychologist; Children's Hospital of
Pittsburgh's William J. Doyle; University of British Columbia's Gregory
E. Miller; University of Pittsburgh School of Medicine's Bruce S. Rabin
and Ellen Frank; and the University of Virginia Health Sciences Center's
Ronald B. Turner.
The National Center for Complementary and Alternative Medicine,
National Institute of Mental Health, National Heart, Lung and Blood
Institute and the MacArthur Foundation Research Network on Socioeconomic
Status and Health funded this research.
Journal Reference:
- Sheldon Cohen, Denise Janicki-Deverts, William J. Doyle, Gregory E. Miller, Ellen Frank, Bruce S. Rabin, and Ronald B. Turner. Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk. PNAS, April 2, 2012 DOI: 10.1073/pnas.1118355109
Courtesy: ScienceDaily
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