We all know that stress isn’t good for us. It can cause all sorts of problems in our lives, from making us feel overwhelmed to causing serious health issues. But what many people don’t realise is that stress also has a negative impact on our immune system. In this article, we will discuss the relationship between stress and the immune system, as well as the effects that stress can have on our overall health.

stressed out

What is stress?


The word stress can refer to a multitude of things, both physical and psychological. It’s the body’s response to any type of demand or threat. When you feel threatened, your body releases a hormone called cortisol. Cortisol helps you deal with the situation by giving you extra energy and ensuring that all of your systems are on high alert. This is known as the “fight-or-flight” response

What can cause stress?


There are many different things that can cause stress. Some people may have a high-stress job, while others may experience stress due to their personal relationships. There are also some people who are more sensitive to stress than others.

You may experience physical stressors. These include things like:

causes of stress
  • Injury
  • Disease
  • Surgery
  • Undernourishment
  • Dehydration
  • Extremes of temperature (in either direction)

Stress can also be caused by physiological factors. This is when an individual perceives that the demands placed upon them exceed or even simply threaten to exceed their capacity to cope. This might simply be because of unhealthy relationships at work (e.g. nasty boss or bullying colleagues) or at home, a person’s financial circumstances or the kids are playing up.

caveman fight or flight

Why does stress exist?


In short, anything that puts demands on us can be a stressor. Now, not all stress is bad. Good stress, or eustress, can actually motivate us and help us to achieve things. It’s the bad kind of stress or distress that we need to worry about, as it’s this that will have an impact on our immune system.

The purpose of the stress response is to allow us to cope swiftly and effectively in response to life-threatening situations. Biologically our system switches from long term to short term survival priorities.

Biological resources are then channelled to systems that require them when responding to the challenge.

The stress response is delivered by the sympathetic nervous system and also by a system known as the hypothalamus-pituitary-adrenal axis (the HPA axis). The sympathetic nervous system is activated within 20-30 seconds of being confronted by a stressor.

Once upon a time, this was appropriate when you were faced with a sabre-toothed tiger; but it is not the best response to the pressures of day to day life. This activation will subside within one hour of the stressor going away.

On the other hand, the HPA axis is much slower and can take from minutes to hours to respond, with its effects lasting days or weeks. This HPA axis is responsible for the release of the stress hormone cortisol, whose chief purpose is to convert the body’s energy stores into a form that is ready for immediate use.

How does stress affect the immune system?


The immune system is a complex network of cells, tissues, and organs that work together to protect the body from infection. The first line of defence against invading pathogens is the barrier defences, such as skin and mucous membranes, which prevent viruses and bacteria from entering the body.

immune system

The cortisol released when stressed will alter the disruption of and movement of white blood cells throughout the body, block the production of new lymphocytes, cause the destruction of other lymphocytes, and suppress the production of cytokines. Lymphocytes and cytokines, amongst others, are essential for a well-balanced immune system which, given the increasing prevalence of Covid-19, is essential for us all.

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