What is stress, anyway?

Stress has become a common word in today’s language but most people use it incorrectly and without full knowledge of what it implies.

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In the beginning

The study of stress dates back at least to the early work of Hans Selye, who first discovered the body’s stress response in the early 1930′s.

Selye found that the hormonal response of laboratory rats to various different hormone treatments, poisons, heat and cold treatments and traumas was the same in each case.  He published a paper about this phenomenon called “A syndrome produced by various nocuous agents” in 1932.  The abstract of this paper reads:

“Experiments on rats show that if the organism is severely damaged by acute non-specific nocuous agents such as exposure to cold, surgical injury, production of spinal shock (transcision of the cord), excessive muscular exercise, or intoxications with sublethal doses of diverse drugs (adrenaline, atropine, morphine, formaldehyde, etc.), a typical syndrome appears, the symptoms of which are independent of the nature of the damaging agent or the pharmacological type of the drug employed, and represent rather a response to damage as such.”

Selye had inadvertently discovered that the body’s alarm response mechanism to any hormonal, physical or psychological stress is basically the same.  Later research would find that there are subtle differences in the way that the body responds to physical and psychological stresses, and even between various types of psychological stress, but the fundamental principle still applies.

However, at this early stage, none of this was known and what’s more, neither the term “stress” nor the idea of the General Adaptation Syndrome were used.  These came later on.  Let’s look at those now.

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Stress and the General Adaptation Syndrome

Around ten years after he described his first findings, Hans Selye wrote a detailed description of the General Adaptation Syndrome, called “The General Adaptation Syndrome and the diseases of adaptation“.  This syndrome included the alarm response to a stressor and two other stages, as follows:

• Alarm reaction – this is where the body responds to acute stress and often occurs in tandem with the fight-or-flight response
• Resistance – during which the mobilization of the various coping mechanisms is maximized
• Exhaustion – in which continued exposure to the stressor results in destructive damage or death.  This stage looks very similar to the alarm reaction stage and is reached when the organism undergoes chronic stress

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The modern model of acute and chronic stress

These days, most students of stress don’t like this model particularly and instead look at stress in two scenarios:

1. Acute stress - when the body is subjected to a sudden, acute stress, which includes undergoing the fight or flight response; and
2. Chronic stress - when the body is subjected to chronic stress and becomes ill as a result.

Acute stress is easier to measure, understand and describe because we can all instantly relate to that sweaty-hands, beating heart sensation.  Chronic stress is another kettle of fish entirely. Broadly speaking, however, these two phases of stress correspond to two hormonal pathways that are activated, to varying degrees, by stressors:

• Adrenaline – the release of adrenaline in the fight-or-flight response
• Cortisol - the production of cortisol through the hypothalamic-pituitary-adrenocortical (HPA) axis

At this point, however, we are still a little unclear about what is even meant by stress!  Fortunately, some sort of clarification is on the horizon…

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Stress, stressors and terminology

As the new research into the concept of stress began to kick off in earnest, The godfather of stress, Hans Selye, was criticised for not being clear about the definitions.

He therefore decided to use the term “stressor” to refer to the stimulus and the term “stress” to refer to the response.  This was unfortunate, as the term “stress” in any other context refers to the cause of the problem and the term “strain” is used to describe the response.

For example, in mechanical engineering, the term stress refers to the load on the bridge and the term strain refers to the amount that the bridge suffers as a result of bearing the load.

However, by the time the nomenclature was tidied up, the term “stress” had been used too many times to refer to the response of the organism and the rest, as they say, is history…

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A clarification of what stress means

In his book, The Stress of Life, Selye lists a number of things that do not define stress, as follows.  He says that stress is not:

1. Nervous tension
2. Discharge of adrenaline in the fight or flight response
3. Discharge of cortisol in the HPA axis
4. The non-specific result of damage
5. Deviation from homeostasis
6. Anything that causes an alarm reaction
7. The General Adaptation Syndrome
8. A non-specific set of phenomena
9. A phenomenon with a specific cause
10. Bad for our health
11. Avoidable

Selye suggests that stress is the common denominator of the body’s response mechanisms, or the set of non-specific changes that occur in the body in response to a stressor.

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The perception of stress

Richard Lazarus argued that for a stressor to create stress in the body, it has to be perceived as such.  This is particularly relevant for psychological stressors but, equally, can be applied to physical stressors as well.  This is one of the reasons why anaesthetic is so important for operations.

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Background to the fight-or-flight response

Although the concept of stress and the way in which an organism responds to being in a state of stress was not fully teased out by Selye until the mid-1940′s, the fight or flight response had been described significantly earlier, by Walter Bradford Cannon.  And it is a key part of the stress response.

In 1915, Cannon coined the expression “fight or flight” when he wrote the book ”Bodily Changes in Pain, Hunger, Fear and Rage: An Account of Recent Researches into the Function of Emotional Excitement.”

The interesting thing is that Cannon recognised the alarm phase of the acute stress response as a result of psychological stimuli – threats – but Selye recognised the alarm phase in response to physical stimuli – poisons and trauma.

And despite writing about 100 years ago, Cannon even went so far as to identify and write extensively about the various components of the fight-or-flight response, including the role of the adrenals, the release of glucose and the improvement of skeletal muscle contraction (strength).

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What’s next?

Next week, I’m going to look at the nitty-gritty of how stress affects us, including looking at the ominously-named HPA-axis.  After that, I’ll review why stress makes us sick and then consider why stress makes us fat.  Finally, to end on a positive note, I’ll take a look at what we can do to reduce the stress in our lives.