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June 3, 2025

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Shared with permission from The Conversation banner.

It has been a long winter, filled with many viruses and cost-of-living pressures, on top of the usual mix of work, study, life admin and caring responsibilities.

Stress is an inevitable part of life. In short bursts, our stress response has evolved as a survival mechanism to help us be more alert in fight or flight situations.

But when stress is chronic, it weakens the immune system and makes us more vulnerable to illnesses such as the common cold, flu and COVID.

Stress makes it harder to fight off viruses

When the immune system starts to break down, a virus that would normally have been under control starts to flourish.

Once you begin to feel sick, the stress response rises, making it harder for the immune system to fight off the disease. You may be sick more often and for longer periods of time, without enough immune cells primed and ready to fight.

In the 1990s, American psychology professor Sheldon Cohen and his colleagues conducted a number of studies where healthy people were exposed to an upper respiratory infection, through drops of virus placed directly into their nose.

These participants were then quarantined in a hotel and monitored closely to determine who became ill.

One of the most important factors predicting who got sick was prolonged psychological stress.

Cortisol suppresses immunity

“Short-term stress” is stress that lasts for a period of minutes to hours, while “chronic stress” persists for several hours per day for weeks or months.

When faced with a perceived threat, psychological or physical, the hypothalamus region of the brain sets off an alarm system. This signals the release of a surge of hormones, including adrenaline and cortisol.

Graphic of the human brain.
The hypothalamus sets off an alarm system in response to a real or perceived threat. Image: Canva

In a typical stress response, cortisol levels quickly increase when stress occurs, and then rapidly drop back to normal once the stress has subsided. In the short term, cortisol suppresses inflammation, to ensure the body has enough energy available to respond to an immediate threat.

But in the longer term, chronic stress can be harmful. A Harvard University study from 2022 showed that people suffering from psychological distress in the lead up to their COVID infection had a greater chance of experiencing long COVID. They classified this distress as depression, probable anxiety, perceived stress, worry about COVID and loneliness.

Those suffering distress had close to a 50% greater risk of long COVID compared to other participants. Cortisol has been shown to be high in the most severe cases of COVID.

Stress causes inflammation

Inflammation is a short-term reaction to an injury or infection. It is responsible for trafficking immune cells in your body so the right cells are present in the right locations at the right times and at the right levels.

The immune cells also store a memory of that threat to respond faster and more effectively the next time.

Initially, circulating immune cells detect and flock to the site of infection. Messenger proteins, known as pro-inflammatory cytokines, are released by immune cells, to signal the danger and recruit help, and our immune system responds to neutralise the threat.

During this response to the infection, if the immune system produces too much of these inflammatory chemicals, it can trigger symptoms such as nasal congestion and runny nose.

Woman with a runny nose.
Our immune response can trigger symptoms such as a runny nose. Image: Canva

What about chronic stress?

Chronic stress causes persistently high cortisol secretion, which remains high even in the absence of an immediate stressor.

The immune system becomes desensitised and unresponsive to this cortisol suppression, increasing low-grade “silent” inflammation and the production of pro-inflammatory cytokines (the messenger proteins).

Immune cells become exhausted and start to malfunction. The body loses the ability to turn down the inflammatory response.

Over time, the immune system changes the way it responds by reprogramming to a “low surveillance mode”. The immune system misses early opportunities to destroy threats, and the process of recovery can take longer.

So how can you manage your stress?

We can actively strengthen our immunity and natural defences by managing our stress levels. Rather than letting stress build up, try to address it early and frequently by:

1) Getting enough sleep

Getting enough sleep reduces cortisol levels and inflammation. During sleep, the immune system releases cytokines, which help fight infections and inflammation.

2) Taking regular exercise

Exercising helps the lymphatic system (which balances bodily fluids as part of the immune system) circulate and allows immune cells to monitor for threats, while sweating flushes toxins. Physical activity also lowers stress hormone levels through the release of positive brain signals.

3) Eating a healthy diet

Ensuring your diet contains enough nutrients – such as the B vitamins, and the full breadth of minerals like magnesium, iron and zinc – during times of stress has a positive impact on overall stress levels. Staying hydrated helps the body to flush out toxins.

4) Socialising and practising meditation or mindfulness

These activities increase endorphins and serotonin, which improve mood and have anti-inflammatory effects. Breathing exercises and meditation stimulate the parasympathetic nervous system, which calms down our stress responses so we can “reset” and reduce cortisol levels.The Conversation


Sathana Dushyanthen, Academic Specialist & Lecturer in Cancer Sciences & Digital Health| Superstar of STEM| Science Communicator, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Top image: Canva

  • I will also add to the above and say that a great preventative measure is taking a sick day if you are feeling sick and also having a nap on the weekend if you live a busy life. I find that that sets me up for the week and helps me not be so tired!


  • Thank you for sharing this really great article. Stress is a huge cause of many health issues and inflammation is one of them. Stress always makes your body run down leaving you prone to getting sick. I have started to be more aware of my stress level and try to ease them as soon as i can feel it start as life can be overwhelming at times. Getting enough sleep is so important but is not always easy to do especially if you are experiencing insomnia regularly.


  • This is a fantastic article. Chronic stess is definitely not good for your health. I’ve always noticed that if I get stressed out I end up unwell and the more I rest and look after my body/mind the faster I heal. I’ve learnt its easier just to manage stress and look after myself in the first place.


  • I am a constant stresser and worrier and have to reign it in. It’s too easy to get tied up in what ifs and how comes. Concentrating on other things to take my mind off them is they key. Reading a good book, exercising. Things that can occupy my mind.


  • Very informative article and one that I drew a lot from. When I was 17 I read the back of a bus ticket and it said ‘Worry is interest on trouble due’ this little quote has stuck with me for over 30 years! I try very hard not to worry about things that have not happened yet. If I find myself getting stressed over something I just say to myself ‘will this matter in 6 months time’. More often than not, the answer is no. I am a pretty chill person which probably helps explain why I do not get sick very often at all.


  • Really insightful article that makes it much more easy to understand! I can definitely tell when im feeling more run down, tired, lack of sleep and stressed that getting ill seems to somewhat come creeping and makes it easier for me to feel unwell. Im dreading the winter cold and flu but definitely trying to keep our family warm, rested and healthy!


  • This is so true! Every time I feel stressed or under a lot of pressure my body is like nope, you’re getting sick now. In a way if forces me to relax but also makes it harder to compete whatever it is is stressing me. I think this shows the importance of self-care to prevent burn out and illness.


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