The stress response

What is the stress response?

The stress response is a natural survival mechanism to mobilise the body, giving immediate energy to fight or run away when we encounter a dangerous situation. This response is essential for our survival.

When the threat is over, and the stress hormones are used up or expelled, the body enters a recovery phase where it rests and rebuilds its energy stores for the next time a stress response is needed.

When the stress response is constantly activated, in situations where it is not needed, it takes a toll on the body, leading to problems such as high blood pressure, heart disease, and anxiety disorders.

Understanding how the stress response works is essential to managing it effectively and preventing unnecessary anxiety.

Walter Bradford Cannon first defined the stress response in 1915. In his research, he discovered that the body similarly responds to stressful stimuli, regardless of the source of the stressor, which means your body will respond the same way to a worrisome thought as walking out in front of a car. This is an important point for people with anxiety disorders and shall be explained later in the article.

Hans Selye (1) was the first to define stress from a biological point of view as “a nonspecific response of the body to any demand made upon it.” In his research, he found three stages of stress: alarm, resistance, and exhaustion.

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The stress response and General Adaption Syndrome GAS

GAS is a three-stage process the body goes through in response to stressors. During the first stage of the alarm reaction, the body prepares for action by releasing hormones. During resistance, the body tries to adapt to the situation. The third stage is exhaustion, when the body’s resources are depleted, and it can no longer maintain its adaptations.

Stage 1 Alarm

The cycle starts with a trigger, which can be anything that causes stress. This trigger activates the hypothalamus, which sets off a chain of events that leads to the release of stress hormones, such as adrenaline and cortisol, from the adrenal glands.

These hormones increase heart rate, blood pressure, and glucose levels. They also divert blood away from non-essential functions, such as digestion, to provide more oxygen and nutrients to muscles so that we can fight or flee from the perceived threat.

If you were strolling up the street and saw a bull, something needs to happen in your body to help you escape danger, i.e. get away from the bull. Your body responds to this type of stressor by giving you the energy and stamina to get away from the bull, i.e., respond to the danger. The alarm bell rings.

This alarm stage, or you might be more familiar with it called the fight-or-flight response, is when the body experiences the physical symptoms of stress.

Your body changes from your stroll to giving you enough energy in your muscles to run without thinking about what to do. You have responded to the immediate danger–the stressor.

Once you spot the bull, this image is sent to your hippocampus and Prefrontal Cortex.
Imagine that your brain has a series of images, and what you see out of the corner of your eye is matched up with some animal that could be dangerous.

The hypothalamus, a tiny region at the base of the brain, sets off an alarm system in the body by waving a metaphorical red flag at the amygdala, and a surge of hormones is released.

  • Adrenaline increases the heart rate, elevates blood pressure, and boosts energy supplies.
  • Cortisol, the primary stress hormone, increases sugars (glucose) in the bloodstream, enhances the brain’s use of glucose, and increases the availability of substances that repair tissues.
  • Cortisol also curbs functions that would be non-essential or harmful in a fight-or-flight situation.

Stage 2 Resistance

The body’s response to stress is resistance. Once the threat has passed, your body repairs itself. When you are out of harm’s way, your body seeks balance, calms your breathing, slows your heart rate, and returns everything to normal. It turns the switch off. Your heart stops pounding, and everything in your body relaxes.

As your body calms down, you remain on high alert, scanning the environment to ensure you are out of danger.  

Calming down while remaining on high alert is vital for people with anxiety disorders, as extended periods of stress, without the benefit of being able to come out of high alert and return to normal, means that you are left with a certain amount of stress.

If your body cannot calm down during the resistance stage, you will enter the third stage of exhaustion.

Stage 3 Exhaustion

If you cannot complete the stress cycle, your body may repeat its stress response.

At the start of this article, I stated that Bradford’s research showed that the body responds similarly to stressful stimuli, regardless of the source of the stressor, which means your body will respond the same way to a worrisome thought as walking out in front of a car.

In this example, with the bull, what I was describing was fear. Both fear and anxiety can give the same feelings, but there are significant differences between the two.

Fear is what you feel when there is an immediate, real danger in your environment, such as a bull.

Anxiety is what you feel when there is no real danger.

In this modern-day world, the stressors that start the process are no longer life-and-death situations. They are worried and remembered stressful situations. In the absence of real danger (the bull), your brain can turn on this ‘switch’ to change your physiology, i.e. your heart rate, breathing etc. (the common symptoms of anxiety).

Anticipating things that could go wrong in the future, such as worrying about work, money, and bills. By thinking or activating fear, using emotional memories (remembered instances in the past when you felt fear or anxiety).

The body responds to what we think. The moment you think you could be in danger, your body will produce a stress response, whether you are in actual danger. The body doesn’t know the difference between genuine and perceived threats. It just responds to the signal that something dangerous might be happening.

Threats in this modern world are someone not replying to your text on time, not having prepared for a deadline, worrying about what other people are thinking about you, and finances.

The more you react to these situations with even a hint of stress, the more likely matches for your hippocampus can make them dangerous.
The alarm bell rings, the stress response starts over again, and your body cannot recover and becomes exhausted.


The stress response is both helpful and necessary. However, if this response is activated in non-life-threatening events, the stress response does not complete, i.e., recovery is impossible.

The changes in the body during a stress response are significant, and your body needs to rest. If you are experiencing stress, there are tips and breathing exercises at the end of this page to help your body recover.


  1. Selye, H. (1953). The General-Adaptation-Syndrome in its Relationships to Neurology, Psychology, and Psychopathology. In A. Weider (Ed.), Contributions toward medical psychology: Theory and psychodiagnostic methods Vol. 1, pp. 234–274). Ronald Press Company.
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