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Stress and the Immune System

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Medically approved by Dr Earim Chaudry
Chief Medical Officer
iconLast updated 11th May 2021
In 30 seconds…

The link between stress and the immune system is complex – and research suggests that stress decreases your ability to tackle infection in many different ways. For example, it reduces the number of lymphocytes – disease-fighting white blood cells – in your blood, whilst disrupting the balance of bacteria in your gut too.

When doctors refer to stress, though, they’re talking about a wide range of psychological phenomena. The nerves you feel before public speaking is stress, but so is long-term exhaustion as well as physical and psychological trauma. Each type of stress affects immune system functioning but can do so in different ways.

Alongside stress itself, our methods of coping with stress can affect the immune system too. Smoking, drinking large quantities of alcohol, and eating poorly can all impair our ability to fight disease.

Stress and the Immune System

Stress is a phenomenon that’s much more common than we might think. According to one survey from 2013, nearly 50% of UK adults described themselves as stressed. A more recent study, from 2018, found that about a third of UK workers were stressed nearly all of the time.

The numbers are huge, and the potential ramifications are fairly serious. This is because stress is not just a feeling that exists in your mind and disappears. Rather, it is a psychological phenomenon that can have profound effects on your body and health.

In this article, we’re looking specifically at the relationship between the immune system and stress – on the ways that stress can impair your body’s ability to fight disease. So, how does stress affect the immune system? Let’s take a look.

What Do We Mean by Stress?

Firstly, let’s be clear on what we mean by stress. The chances are that you recognise it when it occurs. However, researchers have been seeking to pin down its diverse nature for decades.

This is because there’s a vast range of different forms of stress. In its mild form, you might have the stress of brief challenges such as solving a maths question under pressure. Larger challenges like university exams or divorce are likely to be more enduringly stressful. Then there are what scientists call chronic stressors – such as caring for someone who is severely ill, becoming ill yourself, or being a refugee – the effects of which can last for years.

If the range of stresses is huge, very similar physical responses can occur across each of its different forms. It’s thought that these “stressful” events trigger an ancient biological response developed to manage more primitive dangers. As such, the racing heart and sweaty palms we associate with stress have stayed with us since the days when we ran from predators. 

It is these responses, though, that give stress such a significant effect on our immune systems. Whilst we know that stress gives us headaches, increases our blood pressure, and lowers our sex drive, it has effects on systems in our bodies that we might not otherwise notice. Let’s take a look at a few of them.

How Does Stress Affect the Immune System?

The immune system is the name for the complex interaction of organs, tissues, proteins, and cells in the body that help you to fight disease, tackle infection, and stay healthy. It includes processes in lots of different parts of your body – including the skin, the gut, the blood and bone marrow, as well as lymph nodes and the spleen. All play a role in fighting potentially harmful bacteria.

The effects of stress on the immune system are broad – and can actually differ from person to person.

Stress and Lymphocytes

One place where a clear link can be drawn between stress and the immune system is in your body’s production of lymphocytes. A crucial part of your immune system, these are the white blood cells that identify and destroy other cells infected by viruses or bacteria.

In many cases, when you are stressed, your body produces higher quantities of stress hormones known as corticosteroids. These play an important part in your evolutionary “fight or flight” response, but they also tend to suppress the number of lymphocytes in your blood – thus impairing your ability to fight infection.

We say ‘in many cases’ for a reason, though. Whilst a famous study showed that the number of lymphocytes decreased in students undergoing stressful exams, other forms of stress have shown different results. For example, loss and bereavement increase levels of corticosteroids, whilst post-traumatic stress bucks the trend. That form of stress is associated with a reduced number of lymphocyte-blocking hormones.

Stress, Immunity, and the Gut

Your gastrointestinal system is very sensitive to stress – and it is also, perhaps surprisingly, at the frontline of your immune system.

Your gut is home to an astonishing number of bacteria with which your immune system is continuously interacting. The lining of your stomach and intestines is an important place in this interaction – as it prevents any hostile or potentially damaging bacteria from entering into your body at large.

What stress does is weaken the lining of your gut, thus allowing the absorption of bacteria that shouldn’t really be absorbed. This means that your immune system goes into overdrive, causing inflammation when inflammation may not usually have been necessary.

Meanwhile, as the number of lymphocytes is also already lowered by stress, you can be more susceptible to disease as a result.

Inflammation and Stress

Whilst we’ve mentioned inflammation in the gut, stress heightens your inflammatory response in general.

Inflammation is what happens when your immune system responds to an irritant such as a germ. Whilst it is normally a healthy response to infection, it can become overactive when your immune system is not working as it should.

Stress – particular chronic stress – has been seen to cause long-lasting inflammation. And it can cause problems of its own, including arthritis and other autoimmune disorders.

The Indirect Effects of Stress on the Immune System

Finally, it’s not just stress itself that has an effect on your immune system. The ways that we cope with or manage stress can cause problems too.

Smoking cigarettes or consuming large quantities of alcohol are strategies for coping with stress that can have detrimental effects on your immune system. Both reduce a healthy inflammatory response and impair the body’s ability to fight infection.

People who are chronically stressed are more likely to have a poor diet and neglect exercise too – two lifestyle habits that can further impair your immune system.

Key Takeaways

Stress, however common, is not good for our bodies. Because, alongside our quickened pulse and headaches, the effects of stress on the immune system are considerable. It reduces the availability of lymphocytes, the white blood cells that fight disease, and in the long term it increases the inflammatory response – to a potentially dangerous extent.

It’s important to remember that the ways we choose to manage stress affect our immune system too. Smoking and drinking are only the most obvious of these. However, a poor diet – a common response to stress – can have a similar effect too.


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While we've ensured that everything you read on the Health Centre is medically reviewed and approved, information presented here is not intended to be a substitute for professional medical advice, diagnosis, or treatment. It should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.

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