by Daniel Pendick
Copyright © 2002 Memory Loss and the Brain
A little sharpens the mind and memory;
too much shrivels
the brain and makes you sick.
Copyright © Eyewire
|Scores of scientists continue
to explore one of our most basic mental states-stress-and
its effect on the mind and body. The consensus among brain
researchers and psychologists is that a little stress
can be helpful in certain situations, but that too much
can do harm to memory and other basic mental functions.
These findings reiterate the importance of managing stress
throughout life, surfing the healthy wave of mild to moderate
mental stimulation it provides but avoiding the destructive
effects of chronic anxiety.
The Many Faces of Stress
A child rides the roller-coaster for the "rush" of adrenaline…
a housebound elderly man stares out of his window day
after day… a nervous university student sits down to take
a final exam… a wilderness guide's pulse quickens as she
hears a twig snap in the brush behind her… a nurse struggles
to stay awake as she begins the 14th hour of her shift…
All these people are experiencing stress in some form,
but with very different consequences. Stress merely means
that the body is marshalling its resources to deal with
a real or perceived threat. A moderate state of stress
makes your brain cells (neurons) crackle, enhancing concentration
and memory. Such moderate, short-term stress can actually
help the student studying for an exam or give a quick
thrill to the child on a roller coaster. But years of
chronic, low-level stress from an unhappy marriage, loneliness,
or depression dulls the mind and promotes chronic diseases
such as hypertension and coronary artery disease-as well
as impairing memory.
Scientists have already mapped out the basic biology of
the body's reaction to stress. When we experience a "stressor"
of any kind-physical or emotional-it triggers a cascade
of chemical events that releases stress hormones into
Researchers are finding that stress hormones affect the
mind as well as the body. This comes from numerous studies
in humans and laboratory animals. For example, when male
lab rats are exposed to an acute stress, they acquire
certain skills better in the following two to three days.
But expose a female rat to the same stressor and they
do not learn as well-possibly due to the effects of the
"female" sex hormone estrogen.
One of the researchers who has done many of these experiments
is Tracey Shors, Ph.D., associate professor of psychology
and neuroscience at Rutgers University. The connection
between acute stress and learning-not yet demonstrated
in humans-could confer some sort of advantage, Shors speculates.
"You can imagine why a male would learn better after a
short-term stressful experience," she says. "Maybe he
almost got killed, or he almost got eaten by a predator.
In that case, maybe he better pay attention to what's
going on, to where that predator came from, to what tree
he's hiding in, and not go over there again."
It's surprising and as-yet-unknown why the response would
be the opposite in female rats, Shors says. Conceivably,
it could be a way of shutting down procreation when environmental
stress is high. "You could say that's not a good time
to bring young into the world," she says. "But it's all
speculation. All you can really say now is, 'Stress changes
the brain.' I think the fact that males and females react
differently to stress tells you this is not going to be
a simple thing to figure out."
A mind is a terrible thing to stress
And what about you and me? Experience tells us that stress
can have a positive effect on human memory. For example,
a nervous student studying for his exam may actually learn
the material better than his roommate who is less concerned
about the test. This is because the nervous student is
more alert and mentally focused, and thus better able
to perform on a test involving memory and concentration.
However, chronically elevated levels of stress (and stress
hormones) can actually impair the ability to form new
memories and even damage brain cells. One target of chronic
stress on the brain, evidence suggests, is the hippocampus-a
pair of structures that play a key role in the transformation
of experiences and perceptions into enduring memories.
In rats, excess levels of stress hormones impair the growth
and function of cells in the rat hippocampus. Studies
of people with Cushing's
Syndrome-marked by abnormally high secretion of stress
hormones-seem to back this up: people with the syndrome
have trouble recalling paragraphs from memory. Perhaps
not coincidentally, magnetic
resonance imaging (MRI) of their brains show loss,
or atrophy, of cells
in the hippocampus. Other studies also suggest that prolonged
stress can kill or retard the growth and activity of cells
in the hippocampus.
How Much is Too Much?
Not every veteran develops PTSD; many veterans survive
traumatic wartime experiences without needing psychological
help. Even in normal conditions, one person may happily
live a hectic lifestyle that would be intolerably stressful
to another. Everyone's response to stress is unique, determined
by a combination of genes, personality, environment and
personal history. The rat studies by Shors and others
suggest that stress may affect males and females differently.
Aging may also play a role: There's some evidence that
over a lifetime, exposure to stress may gradually increase
stress hormone levels in the blood, possibly contributing
age-related memory impairment. In one recent study,
researchers followed 51 elderly men for up to six years,
classifying them according to how their cortisol rose
or fell. Those who showed a pattern of increasing stress
hormone levels were more likely to high levels were more
likely to show significant cognitive impairments over
the same period.
Elderly people are also at risk for stress from such factors
as social isolation, depression,
and both the physiological and psychological effects of
long-term disease. Such stress can impair memory-mimicking
or worsening cognitive impairment due to such conditions
as early Alzheimer's
Perhaps humans are just not wired to deal with the chronic
and sometimes extreme stresses of modern society. In other
words, we're designed to flee the occasional saber-toothed
tiger-not drive a cab in Manhattan. "You could surmise
in some cases that the stress hormone response evolved
to deal with short, acute experiences," Shors speculates.
"Maybe it isn't equipped to deal with long-term, chronic
stress, and maybe that's why problems arise. The system
just can't maintain that sort of sustained activation."
What You Can Do About It
Fortunately, experiments suggest that reducing the stress
often restores normal brain functions. That means managing
stress-or at least the way you cope with it-may have some
real benefits in the long run. Here are some tips for
reducing stress or coping with it better:
- Relax: Make time throughout the day for a few minutes
of meditation, quiet time, prayer, or even staring
out the window; take a hot bath or go to a movie.
- Exercise: It relieves tension and provides a "time
out" from stressful situations
- Sleep: Get enough of it. It gives your stressed-out
body time to replenish itself.
- Caffeine is a stimulant. Reduce or eliminate caffeine
by cutting back on coffee, tea, caffeinated soda,
- Avoid "multi-tasking," or trying to do more than
one thing at a time, like eating or talking while
- Get organized, set your priorities, and simplify
your life. At work, delegate tasks to others or let
some things go.
- Socialize with family and friends. Limit time spent
with negative people or in stressful situations.
- If you feel that your stress is out of control,
speak to a therapist or ask your doctor whether anti-anxiety
medications might help you as you learn how to manage
Why Zebras Don't Get Ulcers, by Robert M. Sapolsky.
(W.H. Freeman & Co., 1998 (paperback), 434 pp., $16.00).
Renowned stress researcher Sapolsky summarizes research
on the body's response to stress, stress-related disease,
and offers suggestions for how to cope with stress.
"Stress-Coping With Everyday Problems" offers some practical
advice from the National mental health Association. Includes
tips on where to get help with managing your stress. Find
it on the NMHA website: www.nmha.org/infoctr/factsheets/41.cfm
"The neurobiology of stress: from serendipity to clinical
relevance," by Bruce McEwen. (Brain Research, 2000, Volume
886, pp. 172-189.)
"Stress and sex effects on associative learning: for better
or for worse," by Tracey Shors. (The Neuroscientist, 2001,
Volume 4, pp. 353-364.)