What is stress?

Summary: stress is an organism’s reaction to anything that shifts the body out of its allostatic state. More importantly, stress is a survival mechanism orchestrated by the brain. Stress responses have evolved to save you from external threats by adapting to different set points.

Introduction

Stress is an exciting topic and it applies to every living being. Why? Because stress is a mechanism that evolved to keep you alive. As you might recall from my previous post: “Nothing in biology makes sense, except in the light of evolution” – Theodosius Dobzhansky.

Imagine you are about to cross a street and, suddenly, a bus is speeding in your direction. What do you do? One spontaneous reaction is to freeze and potentially get hit by the bus. A more likely reaction, though, is to immediately jump back attempting to save your own life. These opposite, instinctive and stressful reactions are usually referred to as the “fight or flight” response [1]. Contrary to popular belief, stress is also beneficial and often save lives.

Stats and data

However, as you might expect, stress is implicated in many diseases of the mind (e.g. anxiety) and body (e.g. ulcers). For example, a study [2] reported that 74% of the UK population has felt so stressed they were unable to cope or felt overwhelmed. As a result, 29% of participants reported they started drinking (i.e. as a behavioural effect), 51% felt depressed and 32% said they had suicidal thoughts (i.e. as psychological effects).

These data indicate that stress can slowly accumulate damage to one’s body and mind. Furthermore, learning about stress and raising awareness of its effects may alleviate the lives of many people, including yours.

Basic concepts

I have mentioned before, but it is always worth reinforcing key concepts. A working definition of stress refers to ‘an organism’s reaction to a stressor’. A stressor is a biological (e.g. a bacteria) or chemical (e.g. caffeine) agent, environmental condition (e.g. humidity) or external stimuli (e.g. the speeding bus) that shift an organism from its optimal physiological state [3].

For example, an adult’s normal blood pressure in resting-state should be between 90/60mmHg and 120/80mmHg. In the first example (the speeding bus), you would have had an immediate surge in blood pressure to ensure your heart beats faster and delivers oxygen to lower parts of the body.

As a consequence, your blood pressure indirectly produces energy to make you jump and avoid getting hit by the bus. Therefore, a higher blood pressure was not only necessary but also became the optimal level to prevent a tragic circumstance.

Conversely, during sleep, the average adult’s blood pressure is lower than it is during the day. This means that the body is capable of adapting to various setpoints, i.e. different optimal levels, amid changing circumstances in diverse environments.

In other words, the body makes changes according to its needs without any long-term damage (i.e. ulcers or cancer). This process is called allostasis [4] and it receives a significant influence from the brain. Hence, the link with neuroscience. The brain orchestrates the behavioural responses in anticipation of and, adaptation to any event (e.g. the bus speeding in your direction). Thus, in terms of definition, a stressor is anything that knocks your body out of allostasis.

Practice

Can you think of daily things that shift your allostatic balance? Make a list and try understanding why these factors have influence over you? I do not want to spoil the fun, but some examples might involve your work, family reunions, Friday drinks and so on.

Conclusion

This was an introduction to the concept of biological stress. This introductory post should enable you to read future posts in my blog and articles involving stress from a scientific point of view. Furthermore, you should practice to identify external events and stressors that shift your allostatic balance.

Next time I delve into different types of stress and how each of them affect your body.

References:

[1] Fight or flight response – Wikipedia.

[2] The Mental Health Foundation (2018)

[3] Sapolsky, R. M. (2004). Why zebras don’t get ulcers.

[4] Schulkin, J. (2003). Allostasis: a neural behavioral perspective.

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