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How does stress impact your physical health?

King's College London Health Psychology Masters student, Georgia Webb, describes the physiological impact of psychological stress. This draws on the fascinating area of psychoneuroimmunology research.

We’ve all heard generic comments about how stress is bad for us and how we should try to reduce our stress and anxiety levels to better our health. Perhaps you’ve had troubles sleeping lately and have been asked if stress is the reason why, or maybe you’ve been advised by your doctor that you have high blood pressure and need to reduce your stress levels. However, what is not spoken about much is exactly how stress can impact us, and why we should care. So, what does stress do to our bodies?

Stress describes the negative emotions, such as anxiety and sadness, that result from feelings of being overwhelmed by one’s environment. For example, you may feel anxious about finishing a piece of work before a deadline or anticipating an awkward social interaction. There are two types of stress: acute and chronic. Acute stress occurs suddenly and stops quickly, such as randomly bumping into an ex at a party. Chronic stress is longer lasting without a clear end, such as having a stressful job.

Flight or fight response

The flight or fight response describes the bodily reactions that take place when you are in danger. These reactions happen so that you can either run away from the danger or so you can fight it. This response has developed through evolution and these reactions exist to maximise your chance of survival. The flight or fight response releases hormones into the blood stream. One of these hormones is called cortisol.

What does cortisol do?

· Cortisol increases heart rate and respiration

· Cortisol increases blood pressure and blood glucose

· Cortisol shuts down other body systems that are not needed when you are in danger such as your digestive system

· Cortisol suppresses your immune system by preventing the production of inflammatory mediators so you that can channel as much energy as possible towards fighting or fleeing.

When you experience chronic stress, these hormones are continually released for a long time. Overproduction of cortisol leads to many health implications, some of which are described below.

Slower wound healing

When your immune system is suppressed, your body will take longer to heal. This means that the more stressed you feel, the longer you will take to recover from surgeries and injuries. There is a lot of evidence to demonstrate this effect. For example, a study conducted in 2005, took a group of happily married couples who had been married for an average of 12 years [1]. Every couple attended 2 therapy sessions; the first session was a social support group designed to elicit positive emotions and the second session was a discussion about a marital disagreement designed to elicit stress and conflict. Before each session, a small blister was made on the arm of each person, and after the therapy sessions, their healing rates were assessed. The study found that for each couple, their wounds healed quicker after the social support visit rather than the marital disagreement visit. So, when the couples were anxious, their wounds took longer to heal than when they were happy. Overall, couples who showed higher hostility in their interactions during both therapy sessions healed 60% slower than couples judged to interact more warmly and lovingly. This study demonstrates how stressful situations, both short term (therapy session) and long term (relationship type), can suppress your immune system and prolong healing time.

Further studies have shown that caregivers, who are considered to be a chronically stressed group of people, had a 24% longer healing rate than non-caregivers [2], and that students take 40% longer to heal during exam season than during the summer holidays [3]. These are just a couple of examples of this well-documented phenomenon.

Disease susceptibility

As well as slower wound healing, immune suppression means that you are at a higher risk of catching diseases, viruses and developing infections, and if you do catch a disease your symptoms are more likely to be more severe and for a longer duration. This is very relevant during the pandemic, in which we saw how people with a suppressed immune system were told to shield as they were far more at risk of serious covid-19 complications than people with a fully functioning immune system. If you were chronically stressed during the pandemic, this means that if you did catch covid-19 then it is likely that you would have taken longer to test negative and would have experienced more severe symptoms than if you had felt relaxed and happy.


Stress can trigger headaches. In a study of adolescent girls, those who were classified as experiencing chronic or moderate headaches reported much higher stress levels than those in the low headache category. There are multiple factors that contribute to this. When people are stressed, they tighten their neck and shoulders and clench and grind their jaw, which can lead to muscle compressions resulting in a headache. In addition, other consequences of stress, such as not sleeping, increase the likelihood you will have a headache.


Stress can lead to insomnia. Insomnia is a condition in which you find it hard to fall asleep and when you do sleep you keep waking up. This condition not only leads to extreme fatigue but to a whole host of negative symptoms. Insomnia can lead to headaches and severe difficulties when trying to concentrate or pay attention. This can affect your work or school performance and could even affect your ability to drive and increase the likelihood of being involved in a road collision. Moreover, the fatigue leads to increased irritability, anxiety and depression, creating a vicious cycle in which stress leads to insomnia but insomnia leads to stress.

High blood pressure

Cortisol causes your blood pressure to increase so that your heart can beat faster and get oxygen to your muscles as quickly as possible to help them run or fight. High blood pressure increases your risks of having a stroke, heart disease, heart failure, kidney disease and even dementia. So, although there are few day-to-day symptoms of high blood pressure, it can have a big overall impact on your health.

What about behaviour?

So far, we have talked about how stress directly impacts your physical health, but how you behave as a reaction to feeling stressed can also indirectly lead to health problems. Everyone copes with stress differently and some coping mechanisms are a lot more harmful to our bodies than others.


At university, I saw first-hand how a friend of mine began smoking to cope with the stress of exams. They always said that once exams were over that they would stop smoking but still 3 years later, they are a heavy smoker. Many people start smoking because it provides immediate relief from stress and relaxes them. However, cigarettes contain nicotine which is an addictive substance. The more you smoke the more your body comes to depend on the nicotine. This means that you feel anxious when you cannot smoke, thus adding to the stress you are already feeling. On top of that, smoking increases your likelihood of developing cancer, heart disease, having a stroke, lung disease, diabetes and chronic obstructive pulmonary disease. One study conducted in 2010 followed a group of 419 adults who had been admitted to hospital for a heart attack or for coronary artery bypass surgery[4]. All of these adults claimed that they wanted to stop smoking. The study followed them for a year and found that those who successfully gave up smoking were far less stressed than those who continued smoking. So not only is smoking bad for your physical health, but it actually leads to greater stress in the long run.


Many people when they are stressed skip meals and do not eat enough. This is partly a result of the body’s stress response. Cortisol shuts down our digestive system which leads to appetite suppression. In evolutionary terms, this happens so that the body focuses on the danger at hand and is not distracted by food. Undereating is strongly associated with depression. Chronic undereating can stop your periods, can lead to anaemia (iron deficiency), cause fatigue, and weakens your immune system. On the flip side of the coin, stress can lead to overeating, as people enjoy eating and use it to distract from their negative emotions. Overeating can lead to fat gain which can increase your chances of developing serious health problems such as heart disease, type 2 diabetes, and strokes.

Final Thoughts

In this article I have spoken about some of the ways in which stress affects our physical health and the biological processes underlying these mechanisms. It is important to remember that everyone’s bodies are different, and everyone will react differently to stress. It is also important to remember that stress is a natural part of human life and cannot be avoided all together. But if you are experiencing chronic prolonged stress, you should consider how to reduce this stress to maximise your health and most importantly your happiness.


1. Kiecolt-Glaser, J.K., et al., Hostile marital interactions, proinflammatory cytokine production, and wound healing. Arch Gen Psychiatry, 2005. 62(12): p. 1377-84.

2. Kiecolt-Glaser, J.K., et al., Slowing of wound healing by psychological stress. Lancet, 1995. 346(8984): p. 1194-6.

3. Marucha, P.T., J.K. Kiecolt-Glaser, and M. Favagehi, Mucosal wound healing is impaired by examination stress. Psychosom Med, 1998. 60(3): p. 362-5.

4. Hajek, P., T. Taylor, and H. McRobbie, The effect of stopping smoking on perceived stress levels. Addiction, 2010. 105(8): p. 1466-71.


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