Having a clear idea of the definition of stress will allow you to take the first step on your journey to reduce stress once and for all. Are you suffering from stress? And have you tried many trics and techniques to reduce it? Chances are that you have not been successful. This is not your fault. It is because most experts focus directly on solutions, rather than understanding your problem first. In this respect, it is important to understand what stress is, before trying to find ways how to reduce it. After reading this article you will understand what the definition of stress precisely is: a condition of the body that enables you to deal with problems.

Why knowing the definition of stress is important to reduce stress

Stress. Many seem to suffer from it, few know what it is. To reduce stress, it is important to understand what it is precisely. You will then know why you feel stressed, what stress does to your body and which management techniques you have to adopt to reduce stress. Or even to prevent it.

To reduce stress successfully, it is important to understand what the definition of stress is. Because if you do, then you know what to do to get rid of it, or at least manage it better. You will no longer lose yourself in exercises that are not tailored to your personal situation. You will instead adopt stress management strategies that suit you. You will find it easier to focus on the things you have to do to reduce stress effectively, monitor your progress and stay motivated.

So, without further due, let’s first see what stress precisely is.

The definition of stress

For a proper understanding of what stress really is, we will look first at the historical development of the concept of stress.

The definition of stress: Claude Bernard
The concept of stress started with Claude Bernard in 1865. Unknown author, Public domain, via Wikimedia Commons

For this, we have to go back over 150 years in time, to the year 1865 to be precise. Physiologist Claude Bernard published a now famous study on the role of the liver in secreting glucose formed from glycogen stores. In his publication, he also wrote about his discovery of vascular blood flow regulation by sympathetic nerves in response to different temperatures. While these two topics may at a first glance be miles apart, Claude Bernard used both to develop the concept that the ability of an organism (humans and animals alike) to maintain a constant fluid environment. He figured that temperature to the skin would activate the sympathetic nervous system, which would then liberate glucose from the liver. The internal fluid, he argued, is essential for life independent of the external environment.

As we know now, the activation of the sympathetic nervous system and the liberation of glucose from the liver is one of the stress reactions in the body!

The definition of stress: Walter Cannon
Walter Cannon introduced the concept of "homeostasis", or equilibrium in the body. Perturbation of homeostasis induces stress. Unknown author, CC BY 4.0, via Wikimedia Commons

Claude Bernard’s concept was developed further by Walter Cannon in 1929 and 1939. He invented the term “homeostasis”, which more or less means “equilibrium”. He used this term to describe the maintenance within acceptable ranges of several physiological variables within the internal fluid. These variables include blood sugar, oxygen levels in the blood and body temperature. To maintain homeostasis, or equilibrium, Cannon argued that the body should contain sensors to detect differences between the sensed value of a variable and its set acceptable value. If the two deviate too much, then effectors should come to action to restore the equilibrium.

You may want to compare this mechanism with a thermostat. For example, the body senses temperature constantly, and compares this with a set value of 37 °C. If the sensed temperature is too cold, the body will react by increasing its metabolism of brown fat and shivering. Both increase temperature to take it back to 37 °C. Also, blood vessels in the skin tighten to prevent heat loss, and more blood is diverted to internal organs as a result.

The definition of stress thermostat
Temperature homeostasis. Body temperature is set in the hypothalamus. Detection of perturbation of the set temperature is fed into the hypothalamus, where body temperature is compared with the setpoint. The hypothalamus will then put the nervous system and hormones to work to bring temperature back to what it should be.

In the early 1900s, Cannon described for the first time the acute changes in the activity of the adrenal glands. These are hormone-producing organs that reside on top of the kidneys. These hormones include adrenaline (or epinephrine in the US) and cortisol, which are both released during stress. The acute changes in hormone secretion in response to a perturbation of the equilibrium when facing danger makes “fight-or flight” reactions possible. They allow you to fight off a threat, or to run away from it in order to protect yourself. Cannon rightfully believed that the increased activity of the sympathetic nervous system and the adrenal glands would work together to restore homeostasis. Not only during dangerous times, but also during emotional distress, glucose imbalance, pain or temperature stress.

Are you still with me? If you are, great! If not, suffice it to say that we are on our way to get to the concept of what stress really is. We have already a few pieces of the puzzle in place! These are that the body and its internal fluids are normally in equilibrium (homeostase) and that unbalances in equilibrium are corrected by the body through the sympathetic nervous system and the adrenal glands through the hormone adrenaline (epinephrine).

Now that we are all on the same page, let’s carry on!

The definition of stress Hans Selye
Hans Selye introduced the General Adaptation Syndrome, based on his observations that different stressors cause similar pathologies. Jean-Paul Rioux, CC BY-SA 4.0, via Wikimedia Commons

The next big step to understanding stress was made by Hans Selye in 1956. While experimenting with mice, he observed that different treatments led to very similar results. He found that the mice had enlarged adrenal glands, reduced immune function, and had developed gastrointestinal ulcers. These changes were found to be mediated to a large extent by the steroid hormone cortisol secreted from the adrenal gland. Selye grouped these similar pathologies together under the term “General Adaptation Syndrome”.

Here we have thus a third component of the stress concept: activation of the adrenal gland to secrete the stress hormone cortisol.

It was also Selye who took the term “stress” from the physical world to describe the condition of the body in which one or more variables (temperature, glucose, hormones, emotion, etc.) are out of balance. In other words, stress is a force that needs to be counteracted to restore equilibrium (homeostasis).

Selye thus considered stress a condition of the body, and not a disease in itself. He distinguished three phases of stress:

1. The alarm phase. This is the phase of becoming aware of the threat or disturbed equilibrium (which may occur unconsciously), and is similar to Cannon’s “fight-or-flight” response.

2. The adaptation phase. This is the phase of resistance to the stressor (the factor that causes stress) and the sympathetic nervous system and adrenal gland (adrenaline/epinephrine and cortisol) are activated to restore homeostasis (equilibrium).

3. The exhaustion phase. This phase presents itself only when the adaptation phase has not been successful. Equilibrium has not been restored, and the stress reactions are prolonged. These, according to Selye, can lead to disease (such has immunosuppression and development of gastrointestinal ulcers as he had observed as part of the General Adaptation Syndrome). Eventually, the exhaustion phase can even lead to death. Indeed, Selye’s concept that prolonged stress can produce physical disease and mental disorders is now widely accepted.

We are getting there! We now know that stress is a condition of the body, not a disease, and that the stress reactions in the body (activation of the sympathetic nervous system and the release of epinephrine/adrenaline and cortisol from the adrenal glands) help to restore equilibrium. Also, we know that stress is good for us on the short term, but also that prolonged stress can turn into disease.

Still, there are two questions that remain:

1. Why are stress reactions apparently so similar, while stressors (the things that cause stress) are so different?

2. Are setpoints for physiological and mental variables really strict? If so, there would not be much room for flexibility and adaptation to different circumstances that occur during our daily lives.

These questions bring us to the modern view of stress.

The modern view of stress

The answer to the first question concerning the similarity of stress responses in the light of the multitude of stressor we can encounter every day, was already given by Hans Selye himself. He stated that there are general components to each stressful situation and stress reactions (as in the General Adaptation Syndrome), but also that there must be reactions in the body that are unique to each stressor.

Selye also contributed to answer the second question of fixed or flexible setpoints. In 1956 he introduced the term “heterostasis” (from the Greek “heteros”, meaning other) to describe the establishment of a new equilibrium. This means that the setpoint for a given variable (temperature, pain, hormone or oxygen levels, etc.) can be changed, but only to resist unusually strong stressors that impose high demands on the body to restore homeostasis. This new homeostasis, however, is only attained by treatment with remedies that have no direct curative action but enhance the body’s natural defenses, for example immunization or vaccination to combat viral or bacterial infection.

Although it is fair to say that Selye was on the right track here, in the sense that he was open to the idea that setpoints are not carved in stone, his concept was too simplistic. Later research has found out that setpoints can change, not (only) following medical intervention as Selye proposed, but also naturally.

Indeed, modern stress concepts view stress a consciously or unconsciously sensed threat to homeostasis, which has emerged from the early concepts from Bernard, Cannon and Selye. In contrast to these early concepts, it is now believed that stress responses have a degree of specificity that depends on

·       The particular variable of which the homeostasis is disturbed

·       How the stress is perceived by an individual (some may be bothered by one type of stressor but not by others)

·       The abilities of each individual to cope with a particular stressor

Also, whereas the term “homeostasis” suggests fixed setpoints for physiological and mental variables, these are now recognized to be variable. For example, body temperature naturally changes throughout the day. The same is true for heart rate and blood pressure. They are different when you sleep and rest as compared with when you are awake and walking around.

Therefore, stress reactions themselves can change the values of setpoints themselves, to find a new equilibrium that is optimal for the adaptation to the stressor. For example, your body will change the setpoint for certain parameters when you travel from sea level to places of high altitude (related to oxygen uptake and distribution in the body), or when you go from sunny California to ice-cold Alaska (temperature stress).

To extend the concept of homeostasis and to accommodate the notion of flexible setpoints, Sterling and Eyer introduced the term “allostasis” in 1988. The adaptation of the setpoints is fundamentally different from Selye’ concept “heterosasis”, because allostasis correctly concerns adaptation of setpoints as a natural phenomenon, and not as one that can only be induced by medication.

So here we have it! We now know what the definition of stress is: a condition of the body in which certain variables (be they physical or emotional) are out of balance and that need adaptation to restore equilibrium. The values that define equilibrium may, however, change. This means that stress can induce a new equilibrium to deal with the stressors in the best and most efficient way to protect your health and wellbeing. Paradoxically, stress reactions may induce change through allostatic mechanisms to induce stability!

If adaptations involving allostasis do not play out well, and you do not manage to adapt to the stressor, then your health might be in danger. For example, chronic elevation of blood pressure to ensure adequate blood flow to the brain might eventually lead to atherosclerosis and stroke or coronary occlusion. Risk of such adverse effects has been termed by McEwen in 1998 “allostatic load.” Thus, a high allosteric load refers to stressors that require much effort for the body to restore equilibrium, or to set a new one if that makes adaptation easier or better. These are the stressors that put health at risk. Stressors with a low allosteric load are easier to deal with and will generally not lead to disease.

The definition of stress Bruce McEwen
Bruce McEwen has developed the concept of allostasis and allostatic load to describe all processes in the body that occur at the same time to restore equilibrium or form a new one. If no equilibrium can be reached, than the allostatic load is too high, and sickness may develop. Unknown author, Public domain, via Wikimedia Commons

What can we do now that we understand stress?

Congratulations! You now understand that stress is a condition of the body that helps you to deal with problems. You will thus also understand that stress should not always be looked upon as something negative. Isn't it wonderful that your body has a built-in system that helps you to solve problems? The only downside of stress is that it can damage health if it lasts too long.

It is now time to become more specific as to what the benefits are for you to reduce stress now that you understand what stress is.

Stress reduction can occur on three levels:

1. Treating symptoms to restore or set a new equilibrium

Allostatic stress reactions come in different forms and sizes. Knowing what they are and when they occur makes specific treatment possible. For instance, in the example we mentioned earlier of high blood pressure to supply the brain with more blood, it may help to take medication to reduce blood pressure. In case of psychological stress, you may want to seek psychiatric counsel to restore emotional homeostasis.

2. Identifying stressors

When you know which stress reactions occur, you can easily recognize them, so that you know you are under stress. Most stressors in our human society are of psychosocial nature. Think of problems at work or perhaps in your relationship in your private life. These stressors invariably have an impact on your brain. The brain is the site of the body where stressors are perceived and where the stress reactions are initiated. You should be on the lookout for changes that reflect altered brain function because of stress. For example, you could keep a diary in which you note the quality of your sleep, any concentration problems you might have, or when you feel agitated (just to name a few). Also, you could note accelerated heart rate or increased breathing frequency, and in which circumstances they occur. These alterations are caused by stress hormones, which serve to supply the brain and muscles with more blood to prepare you for fight-or-flight reactions.

3. Reducing stress early or even preventing stress

Finally, the Holy Grail! Understanding stress and realizing what causes it (i.e. the stressors that cause disequilibrium) both help to reduce stress as soon as it presents itself. Or, even better, recognizes the causes before they happen can even prevent stress all together! The latter particularly applies to stress at work, because there are quite a few working conditions known to cause stress. Whenever you see these start to occur, you can immediately intervene and protect your health and that of your colleagues!


As briefly mentioned before, how stressful events are being perceived varies from person to person. Some might be stressed when working in an open workspace, whereas others are not. Some have many abilities to deal with stressors, whereas others have not. The measures to reduce stress will thus depend on the personality of each of us.

In addition, some of you may respond primarily with adrenergic responses, and some may respond rather with cortisol responses to bring about allosteric adaptions to deal with a stressor. This will influence how your body will restore or set a new equilibrium.

Stress sensitivity and stress reactions may depend on:

·       Genetic factors

·       Developmental factors (including upbringing and aging)

·       Previous experiential factors

The technique you will choose to reduce your stress will depend on the stressor at hand, your personality profile, and the type of stress reactions will occur. There is therefore no “one size fits all” solution to reduce stress, as many stress gurus on the Internet seem to promise. This is one of the reasons why most stress reduction programs fail.

How Stressinsight helps

Understanding stress, knowing what causes stress, personality profiles, stress at work…… It may seem complicated to figure all these out by yourself. After all, you may not be a medical doctor, a biologist, a psychiatrist or a business analyst. And certainly not all in one. How on Earth can you figure all of this out efficiently and quickly?

You would have to go through scientific literature and reports written by psychologists and experts in business organization. Many of scientific journals and reports are only available through expensive subscriptions, and are difficult to read for those who are not experts.

A much easier and cheaper way is to consult the Stressinsight membership site. We have gathered all the necessary information for you already, presented in easy-to-read format. You will quickly gain sufficient understanding about stress. You will subsequently use this knowledge to start reducing and preventing stress. The structure of the site is such that we will guide you through the different steps of understanding stress to stress management and stress prevention. While going through the different steps, you will be able to evaluate how you think about stress and stressors, and how you feel as a person.

Why not check the site out, and start reducing stress right now? If you click the sign up button at the top of the page, you can immediately start reading the following 10 articles about understanding stress!

Here are our top 10 studies you can read right now that will help give you a shortcut to understanding stress:

  1. Stress: definition and common causes
  2. How the sympathetic nervous system influences your body during stress
  3. Stress and cortisol
  4. Stress is all about energy in the body
  5. Ending stress: Switching off cortisol
  6. Ending stress: Switching off adrenaline
  7. Psychology of stress
  8. Stress and anxiety, what's the difference?
  9. Habituate or sensitize to stress, that's the question
  10. Why stress is usually not something to worry about