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                          Stress - How Stress Works

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   There are different reasons why stress is bad for your health. Dr Bruce
   McEwen from the Laboratory of Neuroendocrinology at the Rockefeller
   University, New York, lumps the body's reactions to stress together
   under the term "allostasis", which derives from the Greek "allo"
   meaning variable and "stasis" meaning stability.

   Click to Listen Bruce McEwen speaks to The Health Report about
   allostatic load and what stress does to the body.
   Download free Real Audio.

   When challenged, the body releases the stress hormones cortisol and
   adrenaline to help it respond to the threat. These quicken the pulse
   and breathing and increase blood pressure as part of the body's "fight
   or flight" response.

   We need stress hormones to help us to survive, but Dr McEwen says,
   prolonged exposure places an "allostatic load" on the body that can
   also be damaging - lowering the immune system and damaging bones,
   organs and brain cells. For example, someone who is constantly told
   what to do at work, is engaged in continual interpersonal conflict or
   lives in a dangerous neighbourhood and has little control over his life
   is likely to over-produce stress hormones, placing an allostatic load
   on his body and health.

   People with depression, which Dr McEwen says produces similar hormones
   in the body to stress, often suffer a loss of bone material. This is
   presumably related to elevated levels of cortisol and reduced levels of
   other mediators involved with bone metabolism. In chronic depression
   there is often also a loss of muscle mass and an increased deposition
   of fat, especially around the abdomen. Other studies suggest that
   stress hormones also affect body fat, especially abdominal fat. So it's
   likely that chronic stress plays a role in the famous Australian beer
   gut.

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   Genetic factors are also important in determining how your body reacts
   to stress:
     * People with a history of high blood pressure often have elevated
       blood pressure in stress situations that stays elevated after the
       event has passed.
     * Non-insulin dependant diabetics are more sensitive to the effects
       of stress, especially the build-up of body fat and coronary heart
       disease.

   Effects of Chronic Stress
   From animal experiments it is known that high levels of cortisol lead
   to impaired function of the brain with age, and can lead to reduced
   function of the hippocampus and loss of brain cells. Other studies show
   the same results in humans who've led tough lives. Being exposed to
   lots of stress, a high allostatic load and presumably high levels of
   cortisol, causes the body and brain to age more quickly.

   Environmental factors
   Childhood experiences can also affect a person's ability to cope with
   stress throughout their life: A Swedish study showed family conflict
   increases the incidence of insulin-dependent diabetes in children;
   perhaps because the stress affects some of the immune mechanisms
   thought to be responsible for destroying the pancreas. On the other
   hand, events in early life can also have a positive impact. A Canadian
   study demonstrated that newborn animals that are patted and gently
   handled produce lower amounts of cortisol in response to stress than
   others that have less physical contact.


   Stress Hormones and Autoimmunity
   Chronically high stress might be hard on the body, but not enough
   stress hormones can be just as bad. Animal studies suggest that if the
   body doesn't produce enough cortisol this can lead to inflammatory
   disease and autoimmunity, which happens when the immune system attacks
   the body itself. So people who suffer from autoimmune diseases such as
   arthritis or multiple sclerosis perhaps don't produce enough cortisol
   to keep their immune systems healthy.

   Good Stress
   Ironically, while prolonged stress is bad your health, short bursts of
   acute stress can be good for you...

                   home   control   good stress   glossary

                                   The Lab
                (c) 1998 Australian Broadcasting Corporation