The newsletter of the Memory Disorders Project at Rutgers University

Experience a "stressor"

When we experience a "stressor" of any kind-physical or emotional-it triggers a cascade of chemical events that releases stress hormones into the bloodstream. It works this way:      

1. You experience a "stressor." The stimulus may be external-like a physical threat, the death of a loved one, or pressure at work. Or it may also be internal, like an illness or metabolic disorder.

2. The first response comes from the adrenal glands, perched atop the kidneys, which release a chemical called adrenaline. Adrenaline rushes throughout the body and throws a series of cellular switches that get you ready to fend off that saber-toothed tiger, mugger, or obnoxious coworker. It's called the fight-or-flight response: The heartbeat and breathing quicken; blood pressure rises; the liver releases stored blood sugar (glucose) to provide energy; and blood flow is diverted to the brain and major muscles as energy and blood flow are diverted away from "non-essential" processes such as digestion, growth, reproduction, and tissue repair.

3. Maybe 10 minutes after the stressor, a second response occurs. A brain area called the hypothalamus releases a chemical messenger, corticotrophin-releasing factor (CRF). This stimulates the pituitary gland at the base of the brain to secrete adrenocorticotrophin (ACTH), which rides the bloodstream to the adrenal glands, which secrete so-called "stress hormones" called glucocorticoids. These chemicals, chiefly cortisol, disperse into the body, setting off many different processes. They also cause effects in the brain.              

Here are some indications that you are experiencing unhealthy levels of stress:      

- You feel irritable

- You have trouble sleeping, or sleep too much.

- You lose your appetite or can't stop eating.

- You have trouble with relationships (i.e.., getting along with family & friends

These may also be signs of depression, which in itself is a form of stress. Seek out a professional diagnosis.

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.

Raging Hormones

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 the bloodstream.

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 to 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 disease.

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, and chocolate;
  • Avoid "multi-tasking," or trying to do more than one thing at a time, like eating or talking while driving;
  • 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 stress better.


  • 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:
  • "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.)