Stress and Disease
Stress and Disease: New Perspectives By Harrison Wein, Ph.D.
For thousands of years, people believed that stress made you sick. Up until
the nineteenth century, the idea that the passions and emotions were intimately
linked to disease held sway, and people were told by their doctors to go to spas
or seaside resorts when they were ill. Gradually these ideas lost favor as more
concrete causes and cures were found for illness after illness. But in the last
decade, scientists like Dr. Esther Sternberg, director of the Integrative Neural
Immune Program at NIH's National Institute of Mental Health (NIMH), have been
rediscovering the links between the brain and the immune system.
The Immune System and the Brain
When you have an infection or something else that causes inflammation such as
a burn or injury, many different kinds of cells from the immune system stream to
the site. Dr. Sternberg likens them to soldiers moving into battle, each kind
with its own specialized function. Some are like garbage collectors, ingesting
invaders. Some make antibodies, the "bullets" to fight the infectious
agents; others kill invaders directly. All these types of immune cells must
coordinate their actions, and the way they do that is by sending each other
signals in the form of molecules that they make in factories inside the cell.
"It turns out that these molecules have many more effects than just being
the walkie-talkie communicators between different kinds of immune cells," Dr.
Sternberg says. "They can also go through the bloodstream to signal the brain
or activate nerves nearby that signal the brain."
These immune molecules, Dr. Sternberg explains, cause the brain to change its
functions. "They can induce a whole set of behaviors that we call sickness
behavior. . . . You lose the desire or the ability to move, you lose your
appetite, you lose interest in sex." Scientists can only speculate about the
purpose of these sickness behaviors, but Dr. Sternberg suggests that they might
help us conserve energy when we're sick so we can better use our energy to
fight disease.
These signaling molecules from the immune system can also activate the part
of the brain that controls the stress response, the hypothalamus. Through a
cascade of hormones released from the pituitary and adrenal glands, the
hypothalamus causes blood levels of the hormone cortisol to rise. Cortisol is
the major steroid hormone produced by our bodies to help us get through
stressful situations. The related compound known as cortisone is widely used as
an anti-inflammatory drug in creams to treat rashes and in nasal sprays to treat
sinusitis and asthma. But it wasn't until very recently that scientists
realized the brain also uses cortisol to suppress the immune system and tone
down inflammation within the body.
Stress and the Immune System
This complete communications cycle from the immune system to the brain
and back again allows the immune system to talk to the brain, and the brain to
then talk back and shut down the immune response when it's no longer needed.
"When you think about this cross-talk, this two-way street," Dr.
Sternberg explains, "you can begin to understand the kinds of illnesses that
might result if there is either too much or too little communication in either
direction."
According to Dr. Sternberg, if you're chronically stressed, the part of the
brain that controls the stress response is going to be constantly pumping out a
lot of stress hormones. The immune cells are being bathed in molecules which are
essentially telling them to stop fighting. And so in situations of chronic
stress your immune cells are less able to respond to an invader like a bacteria
or a virus.
This theory holds up in studies looking at high-levels of shorter term stress
or chronic stress: in caregivers like those taking care of relatives with
Alzheimer's, medical students undergoing exam stress, Army Rangers undergoing
extremely grueling physical stress, and couples with marital stress. People in
these situations, Dr. Sternberg says, show a prolonged healing time, a decreased
ability of their immune systems to respond to vaccination, and an increased
susceptibility to viral infections like the common cold.
Some Stress is Good
People tend to talk about stress as if it's all bad. It's not.
"Some stress is good for you," Dr. Sternberg says. "I have to get my
stress response to a certain optimal level so I can perform in front of an
audience when I give a talk." Otherwise, she may come across as lethargic and
listless.
But while some stress is good, too much is not good. "If you're too
stressed, your performance falls off," Dr. Sternberg says. "The objective
should be not to get rid of stress completely because you can't get rid of
stress - stress is life, life is stress. Rather, you need to be able to use
your stress response optimally."
The key is to learn to move yourself to that optimal peak point so that you're
not underperforming but you're also not so stressed that you're unable to
perform. How much we're able to do that is the challenge, Dr. Sternberg
admits. This may not be possible in all situations, or for all people, because
just as with the animals Dr. Sternberg studies, some people may have a more
sensitive stress response than others.
"But your goal should be to try to learn to control your stress to make it
work for you," Dr. Sternberg says. "Don't just think of getting rid of
your stress; think of turning it to your advantage."
Controlling the Immune Response
Problems between the brain and the immune system can go the other way, too.
If for some reason you're unable to make enough of these brain stress
hormones, you won't be able to turn off the immune cells once they're no
longer needed.
"There has to be an exit strategy for these battles that are being fought
by the immune system, and the brain provides the exit strategy through stress
hormones," Dr. Sternberg says. "If your brain can't make enough of these
hormones to turn the immune system off when it doesn't have to be active
anymore, then it could go on unchecked and result in autoimmune diseases like
rheumatoid arthritis, lupus, or other autoimmune diseases that people recognize
as inflammation."
Dr. Sternberg says that there are several factors involved in these
autoimmune conditions. There are many different effects that the brain and its
nervous system can have on the immune system, depending on the kinds of nerve
chemicals that are being made, where they're being made, what kind of nerves
they come from, and whether they're in the bloodstream or not. Still, at least
part of the problem in these diseases seems to involve the brain's hormonal
stress response.
"So if you have too much stress hormone shutting down the immune response,
you can't fight off infection and you're more susceptible to infection,"
Dr. Sternberg concludes. "Too little stress hormones and the immune response
goes on unchecked and you could get an inflammatory disease."
Pinpointing the Problems
Why these miscommunications between the brain and the immune system come
about is still largely unknown, and involves many genes and environmental
factors. But by studying animals, scientists have finally been able to start
understanding how the miscommunications occur.
Dr. Sternberg first started publishing work on the links between the brain
and the immune system back in 1989 studying rats with immune problems. "In
many of these cases it's very hard to show the mechanism in humans," Dr.
Sternberg explains, "but you can show the mechanism in animals because you can
manipulate all the different parts of the system and you can begin to understand
which parts affect which other parts." It has taken "a good ten years" to
gather enough evidence in human studies to show that the principles her lab
uncovered in rats were also relevant to human beings.
Drugs that have been tested in rats to correct brain/immune system problems
have had unpredictable effects. That is because nothing happens in isolation
when it comes to the brain and the immune system. Dr. Sternberg points out that
our bodies are amazing machines which at every moment of the day are constantly
responding to a myriad of different kinds of stimuli - chemical,
psychological, and physical. "These molecules act in many different ways in
different parts of the system," she says. Understanding how the brain and the
immune system work together in these different diseases should help scientists
develop new kinds of drugs to treat them that would never have occurred to them
before.
Taking Control Now
Dr. Sternberg thinks that one of the most hopeful aspects of this science is
that it tells us it's not all in our genes. A growing number of studies show
that, to some degree, you can use your mind to help treat your body. Support
groups, stress relief, and meditation may, by altering stress hormone levels,
all help the immune system. For example, women in support groups for their
breast cancer have longer life spans than women without such psychological
support.
There are several components of stress to think about, including its
duration, how strong it is, and how long it lasts. Every stress has some effect
on the body, and you have to take into account the total additive effect on the
body of all stressors when considering how to reduce stress.
Perhaps the most productive way to think about stress is in terms of control.
Dr. Sternberg shows a slide of an F-14 jet flying sideways by the deck of an
aircraft carrier, its wings completely vertical. "The Navy Commander who flew
that jet told me that he was the only one in the photo who was not stressed, and
that's because he was the one in control. The officer sitting in the seat ten
feet behind him was in the exact same physical situation but was not in control.
Control is a very important part of whether or not we feel stressed.
So if you can learn to feel that you're in control or actually take control
of certain aspects of the situation that you're in, you can reduce your stress
response." Studies show that gaining a sense of control can help patients cope
with their illness, if not help the illness itself.
Until science has more solid answers, it can't hurt to participate in
support groups and seek ways to relieve stress, Dr. Sternberg says. But what you
need to remember is if you do these things and you're not successful in
correcting whatever the underlying problem is, it's not your fault because
there's a biology to the system. "You need to know the benefits of the
system," she says, "but its limitations as well." In other words, try not
to get too stressed about being stressed.
A Word to the Wise...
Stress Control First try to identify the things in your life that cause you
stress: marital problems, conflict at work, a death or illness in the family.
Once you identify and understand how these stressors affect you, you can begin
to figure out ways to change your environment and manage them.
If there's a problem that can be solved, set about taking control and
solving it. For example, you might decide to change jobs if problems at work are
making you too stressed.
But some chronic stressors can't be changed. For those, support groups,
relaxation, meditation, and exercise are all tools you can use to manage your
stress. If nothing you do seems to work for you, seek a health professional who
can help. Also seek professional help if you find that you worry excessively
about the small things in life.
Keep in mind that chronic stress can be associated with mental conditions
like depression and anxiety disorders as well as physical problems. Seek
professional help if you have:
- Difficulty sleeping
- Changes in appetite
- Panic attacks
- Muscle tenseness and soreness
- Frequent headaches
- Gastrointestinal problems
- Prolonged feelings of sadness or worthlessness
Source: National Institutes of Health "Word on
Health"
Last Editorial Review: 4/6/2006
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