Stress

What is stress?

Stress is simply a fact of nature -- forces from the outside world affecting the individual. Hence, all living creatures are in a constant interchange with their surroundings (the ecosystem), both physically and behaviorally. This interplay of forces, or energy, is of course present in the relationships between all matter in the universe, whether they are living (animate) or not living (inanimate). However, there are critical differences in how different living creatures relate to their environment. These differences have far reaching consequences for survival. Because of the overabundance of stress in our modern lives, we usually think of stress as a negative experience. But from a biological point of view, stress can be neutral, negative, or positive.

Stress has driven evolutionary change (the development and natural selection of species over time). Thus, the species that adapted best to the causes of stress (stressors) have survived and evolved into the plant and animal kingdoms we now observe. Man, because of the evolution of the human brain, especially the part called the neo-cortex, is the most adaptive creature on the planet. This adaptability is largely due to the changes and stressors that we have faced and mastered. Therefore, we, unlike other animals, can live in any climate or ecosystem, at various altitudes, and avoid the danger of predators. Moreover, most recently, we have learned to live in the air, under the sea, and even in space, where no living creatures that we know of have ever survived. So then, what is so wrong with stress?

A brief history of stress

A key to the understanding of the negative aspects of stress is the concept of milieu interiur (the internal environment of the body), which was first advanced by the great French physiologist, Claude Bernard. In this concept, he described the principles of dynamic equilibrium. In dynamic equilibrium, constancy, a steady state (situation) in the internal bodily environment, is essential to survival. Therefore, external changes in the environment or external forces that change the internal balance must be reacted to and compensated for if the organism was to survive. Examples of such external forces include temperature, oxygen concentration in the air, the expenditure of energy, and the presence of predators. In addition, diseases were also stressors that threatened the constancy of the milieu interiur.

The great neurologist, Walter Cannon, coined the term "homeostasis" to further define the dynamic equilibrium that Bernard had described. He was also the first to recognize that stressors could be emotional as well as physical. Through his experiments, he demonstrated the "fight or flight" response that man and other animals share when threatened. Further, Cannon traced these reactions to the release of a powerful neurotransmitter, called nor-epinephrine (nor-adrenaline), from a part (the medulla) of the adrenal gland. (Neurotransmitters are the body's chemicals that carry messages to and from the nerves.)

Hans Selye, another early scientist of stress, extended Cannon's observations. He included, as part of the body's stress response system, a small gland at the base of the brain, called the pituitary. He described the control by this gland of the secretion of hormones (e.g., cortisol) by the other part (the cortex) of the adrenal gland. Additionally, he actually introduced the term "stress" from physics and engineering and defined it as "mutual actions of forces that take place across any section of the body, physical or psychological."

In his experiments, Selye induced stress in rats in a variety of ways. He found typical and constant psychological and physical responses to the adverse situations that were imposed on the rats. In rats exposed to constant stress, he observed enlargement of the adrenal glands, gastrointestinal ulcers, and a wasting away (atrophy) of the immune (defense) system. He called these responses to stress the general adaptation (adjustment), or stress syndrome. He discovered that these processes, which were adaptive (healthy, appropriate adjustment) and normal for the organism in warding off stress, could become much like illnesses. That is, the adaptive processes, if they were excessive, could damage the body. Here then, is the beginning of an understanding of why stress, really over-stress, can be harmful, and why the word stress has earned such a bad name.

There is now speculation, as well as some evidence, that points to the abnormal stress responses as being involved in causing various diseases or conditions. These include anxiety disorders, depression, high blood pressure, certain ulcers and other gastrointestinal diseases, some cancer, and even aging itself. Stress also seems to increase the frequency and severity of migraine headaches, asthma attacks, and blood sugar fluctuations in diabetics. Overwhelming psychological stress (such as the events of Sept. 11th) can cause both temporary (transient) and long lasting (chronic) symptoms of a serious psychiatric illness called posttraumatic stress disorder (PTSD). (For more information on PTSD, read the posttraumatic stress disorder article.) But, how does a healthy, adaptive response to stress become our enemy?

What is the healthy response to stress?

A key aspect of an adaptational response to stress is the time course. Responses must be initiated rapidly, maintained for a proper amount of time, and then turned off to insure an optimal result. An over-response or the failure to shut off a response can have negative biological consequences to the individual. Healthy human responses to stress involve three components:

The brain handles (mediates) the immediate response. This response signals the adrenal medulla to release norepinephrine.
The hypothalamus (a central area in the brain) and the pituitary gland initiate (trigger) the slower, maintenance response. This response signals the adrenal cortex to release cortisol and other hormones.
Many neural (nerve) circuits are involved in the behavioral response. This response increases arousal (alertness, heightened awareness), focuses attention, inhibits feeding and reproductive behavior, reduces pain perception, and redirects behavior.

The combined results of these three components of the stress response maintain the internal balance (homeostasis), increase energy production and utilization, and alter electrolyte (chemical elements) and fluid balance. They also gear up the organism for a quick reaction through the sympathetic nervous system (SNS). The sympathetic nervous system operates by increasing the heart rate, increasing blood pressure, redirecting blood flow to the heart, muscles, and brain and away from the GI tract, and releasing fuel (glucose and fatty acids) to help fight or flee the danger.

How does the response to stress work?

While the complete story is not fully known, the last 20 years of research has taught us much about how the response to stress works. The two main systems involved are the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system. (These systems are described below.) Triggered (activated) primarily by an area in the brain stem (lowest part of brain) called the locus coeruleus, the sympathetic nervous system secretes nor-epinephrine. The 5 most important concepts to remember about these two systems are:

They are governed by a feedback loop to regulate their response. (In a feedback loop, increased amounts of a substance -- e.g., a hormone -- inhibits the release of more of that substance, while decreased amounts of the substance stimulates the release of more of that substance.)

They interact with each other.
They influence other brain systems and functions.
Genetic (inherited) variability affects the responses of both systems. (That is, depending on their genes, people can respond differently to similar stresses.)
Prolonged or overwhelming responses of these systems can be harmful to an individual.

What is the role of the hypothalamus-pituitary-adrenal (HPA) axis (grouping) in stress?

The HPA axis is a grouping of responses to stress by the brain and the pituitary and adrenal glands. First, the hypothalamus (a central part of the brain) releases a compound called corticotrophin releasing factor (CRF), which was discovered in 1981. The CRF then travels to the pituitary gland, where it triggers the release of a hormone, ACTH. The ACTH is released into the bloodstream and causes the cortex of the adrenal gland to release the stress hormones, particularly cortisol, which is a corticosteroid. Cortisol affects the availability of the fuel supply (carbohydrate, fat, and glucose metabolism), which is needed to respond to stress. However, if cortisol levels stay increased for too long, then muscle breakdown, a decreased inflammatory response, and suppression of the immune (defense) system occur.

Because they suppress the immune system, corticosteroids in measured doses are used to treat many illnesses that are characterized by an overactive immune system, such as asthma and inflammatory bowel disease. For the same reason, they are used to help reduce the chances that our body will immunologically reject a transplanted organ. Corticosteroids also can cause fluid retention and high blood pressure. Therefore, it is critical that the response to corticosteroids be carefully controlled (modulated). This control is usually accomplished by a feedback mechanism in which increased cortisol levels feeding back to the hypothalamus and pituitary turn off production of ACTH. In addition, extremely high levels of cortisol can cause depression and psychosis, which, however, disappear when the levels return to normal.

What is the role of the locus coeruleus in stress?

The locus coeruleus has many connections to other parts of the brain, particularly areas that bring in and process sensory information. (The senses include sight, hearing, smell, taste, and touch.) The locus coeruleus secretes nor-epinephrine and stimulates other brain centers to do the same. It is like the pacemaker (controls the tempo) of the brain. Thus, it increases arousal (heightened awareness, alertness) and vigilance (watchfulness, carefulness), and adjusts (modulates) the action of the autonomic nervous system. The autonomic nervous system regulates blood flow, heart rate, blood pressure, and breathing (respiration). It can also temporarily shut down the gastrointestinal (GI) and sexual systems until the crisis is over. These initial reactions, to get our blood flowing, heart pumping, and muscles energized, occur very quickly and automatically.

How do the connections in the brain work in stress?

The HPA axis and the locus coeruleus systems are linked through the hypothalamus and the brain area known as the limbic system. The limbic system is the control area for emotion and the processing area for memory. These linkages are critical. For example, if you see the bushes rustling, your locus coeruleus immediately starts things (the stress response) rolling. However, then, if you see that it is not a mountain lion, but a golden retriever in the bush, your memory of the tameness of the dog will turn off the stress response. Similarly, if a person is nervous before a public speaking engagement and the first minute or two goes well, this happy feeling will turn down the locus coeruleus. These internal adjustments are why experienced public speakers often start off with a joke. It's as much to calm themselves down (if the joke goes well), as it is to entertain you.

The connections also include the endogenous (within the body) opiate (opium-like) system and the reward (dopamine) system. Thereby, during stress, pain is reduced and an extremely happy feeling (euphoria) may result. These connections partially account for "runner's high" and have a great deal to do with why we like roller coasters and scary movies.

Here's how the connections work. The limbic system performs an emotional analysis and memory review of the information provided by the senses. Then, the multiplicity of connections allows us to determine whether the current stress is:

One that has been mastered in the past and successfully adapted to
Not a threat at all
A clear and present danger

All of this internal activity must occur in milliseconds, and it does.

What do we know about using (activating) and over-using our internal systems that respond to stress?

Animal and human research has taught us much about our internal stress systems. When laboratory animals are exposed to a prolonged stress (usually food deprivation, mild electrical stimulation of the foot, or handling), they develop a stress syndrome. This syndrome consists of high blood pressure (hypertension), loss of appetite, weight loss, muscle wasting, GI ulcers, loss of reproductive function, suppression of the immune system, and depression. Researchers also noticed that long duration (chronic) stress sensitizes (makes more responsive) the stress system. That is, the system then over-responds to new acute stressors. They further noticed that the administration of certain drugs, such as amphetamines or cocaine, could also sensitize the stress response. Moreover, constant stress increases the self-administration of drugs in laboratory animals. So, the more stress there is, the more mice seek the drugs, and the more the sensitivity (increased responsiveness) to stress is increased!

Early separation from the mother has also been seen as another potent stressor in animals. Such separation has been linked to increased levels of the stress hormones that cause the stress syndrome, including depression. Studies in humans are underway to evaluate how maternal stress, even early in the pregnancy, can affect the developing fetus. For example, maternal stress may predispose fetuses to developing depression as children or adults.

Why does maternal stress affect the fetus?

The answer is the shared blood circulation between the mother and the fetus. You see, from the mother's blood, the fetus gets both the good (e.g., nutrients and oxygen) and the bad. The bad components of the blood can include alcohol, nicotine, illicit drugs, prescription drugs, and stress chemicals, such as cortisol and nor-epinephrine.

These animal and human studies seem to indicate that stress leads to depression. In other words, chronic stress in the mother's womb (in utero) or early deprivation (separation from the mother) can predispose a person to developing the psychiatric syndrome of clinical depression in later life. Furthermore, other experiments show that the administration of stress hormones can actually decrease brain connections and even brain cells in crucial areas, such as the limbic system (area of the brain controlling emotion and memory). This loss of brain connections and cells then can lead to further maladaptive (inadequate adjustment) responses to stress.

What's more, some particular kinds of stress seem to be even more detrimental than other types. That is, some types of stress can actually lead to diseases. For example, stresses that are unpredictable and uncontrollable seem to be the greatest culprits. (This is why we don't yet know the full effects of Sept 11th.) On the other hand, stresses with which we can cope and master are not necessarily bad. In fact, we can learn from these stresses, predict their reoccurrence, and develop action plans to reduce or avoid them in the future. In this way, some stresses can actually trigger new personality growth and biologically brought about adaptive (healthy adjustment) changes. Indeed, much of psychotherapy is empirically (guided by practical experience rather than theory) based on this concept. As a matter of fact, many therapists are unaware of the biological processes (mechanisms) that form the basis of their work.

Conclusions about the effects of stress

Uncontrollable, unpredictable, and constant stress has far-reaching consequences on our physical and mental health. Stress can begin in the womb and recur throughout the lifespan. One of the pathological (abnormal) consequences of stress is a learned helplessness that leads to the hopelessness and helplessness of clinical depression. But, in addition, many illnesses, such as chronic anxiety states, high blood pressure (hypertension), heart (cardiovascular) disease, and addictive disorders, to name a few, also seem to be influenced by chronic or overwhelming stress.

Nature, however, has provided us with wonderful processes (mechanisms) to cope with stressors through the HPA axis and the locus coeruleus/sympathetic nervous system. Furthermore, research has shown us the biological processes (mechanisms) that explain what we all intuitively know is true. Which is, that too much stress, particularly when we cannot predict it or control its reoccurrence, is harmful to our health.

How can we manage stress?

If we think about the causes of stress, the nature of the stress response, and the negative effects of some types of stress (prolonged, unexpected, unmanageable), several healthy management strategies become clear. First, exercise. You see, since the stress response prepares us to fight or flee, our bodies are primed for action. Unfortunately, however, we usually handle our stresses while sitting at our desk, standing at the water cooler, or behind the wheel stuck in traffic. Exercise on a regular basis helps to burn off and use up the stress hormones and neurochemicals. Thus, exercise can help avoid the damage to our health that prolonged stress can cause. In fact, studies have found that exercise is a potent anti-depressant, anxiolytic (combats anxiety), and sleeping pill for many people, without taking any pills.

For centuries in Eastern religious traditions, the benefits of meditation and other relaxation techniques have been well known. Now, Western medicine and psychology have rediscovered that particular wisdom, translated it into simple non-spiritual methods, and scientifically verified its effectiveness. Thus, one or two 20 to 30 minute meditation sessions a day can have lasting beneficial effects on health. Indeed, advanced meditators can even significantly control blood pressure and heart rate as well.

Elimination of drug use and no more than moderate alcohol use are key to the successful management of stress. We know that people, when stressed, seek these outlets. But, we also know that many of these substances sensitize (make even more responsive) the stress response. As a result, small problems produce big surges of stress chemicals. What's more, these attempts with drugs and alcohol to mask stress often prevent the person from facing the problem directly. Consequently, they are not able to develop effective ways to cope with or eliminate the stress.

In fact, even prescription drugs for anxiety, such as diazepam (Valium), lorazepam (Ativan), or alprazolam (Xanax), can be counterproductive in the same way. Therefore, these medications should only be used cautiously under the strict guidance of a physician. If, however, stress produces a full blown psychiatric problem, like posttraumatic stress disorder (PTSD), clinical depression, or anxiety disorders, then psychotropic medications, particularly the SSRIs, are extremely useful. Examples of the SSRI (selective serotonin reuptake inhibitor) medications include sertraline (Zoloft), paroxetine (Paxil), or fluoxetine (Prozac).

We know that chronic or uninterrupted stress is very harmful. It is important, therefore, to take breaks and decompress. Take lunch and don't talk about work. Take a walk instead of a coffee break. Use weekends to relax and don't schedule so many events that Monday morning will seem like a relief. Learn your stress signals. Take regular vacations, or even long weekends or mental health days, at intervals that you have learned are right for you.

Create predictability in your work and home life as much as possible. Structure and routine in your life can't prevent the unexpected from happening. However, they can provide a comfortable framework from which to respond to the unexpected. Think ahead and try to anticipate the varieties of possibilities, good and bad, that may become realities at work or home. Generate scenarios and response plans. You may find that the "unexpected" really doesn't always come out of the blue. With this kind of preparation, you can turn stress into a positive force to work for your growth and change.

What's in the future for stress?

Stress is part of life and will always be around. The keys to dealing with stress are appropriate control of stressful factors and management of our physical (physiological) and mental (psychological) responses. In this regard, some exciting work is being done on early treatment (intervention) in extremely stressful events (such as Sept. 11th). This intervention, called CISD (critical incident stress debriefing), involves discussing the traumatic event as soon as possible after the event. In fact, CISD can lessen extreme (pathological) reactions to stress and often prevent PTSD in its worst forms from occurring. Hopefully, the concepts of CISD can be translated into helpful strategies for managing the more common (normal) types of stress.

We all have slightly different stress responses because of our genetic make-up. In the future, perhaps, we will be able to alter our genes, for example, if we are genetically determined to be over or under reactors. In fact, the field of pharmacogenetics (medicines that enter the cells' DNA and turn on or off certain genes) is very promising in the area of stress.

Stress At A Glance

Stress is a normal part of life that can either help us learn and grow or can cause us significant problems.
Stress releases powerful neurochemicals and hormones that prepare us for action (to fight or flee).
If we don't take action, the stress response can lead to health problems.
Prolonged, uninterrupted, unexpected, and unmanageable stresses are the most damaging types of stress.
Early separation from a mother can lead to altered stress responses and depression later in life.
The stresses of the mother can affect the stress response of the fetus, and perhaps predispose the child to psychiatric illness later in life.
Stress can be managed by regular exercise, meditation or other relaxation techniques, structured time outs, and learning new coping strategies to create predictability in our lives.
Many of our ways in dealing with stress – drugs, pain medicines, alcohol, smoking, and eating -- actually worsen the stress and can make us more reactive (sensitive) to further stress.
While there are promising treatments for stress, the management of stress is mostly dependent on the willingness of a person to make the changes necessary for a healthy lifestyle.