Stress awareness month – The science behind stress

Stress awareness month been nationally recognized every April since 1992. Even in normal times stress affects the lives of thousands of people. Now with the pandemic still upon is, it is even more relevant to understand the triggers of stress, and what it means for our bodies.

Stress awareness month – The science behind stress
'Stress' by @milie.dsgn for WISE. © 2021 Emilie Schaefer and What Is Science Even?

Stress – we all feel it, we all hate it. Thinking about it just makes it worse! This month is stress awareness month, nationally recognised since 1992. It feels particularly important to discuss stress this year due to the COVID-19 pandemic, putting millions of people under new pressures. Albeit an evolutionary conserved process, and the occasional motivator, long-term stress can take a toll on your mental and physical health. So, what really is stress? What happens inside our bodies when we are stressed? And how do we best handle it? Let us break it down.


What even is stress?

As everyone is affected by stress differently it is difficult to come up with a single definition for stress.

  1. The dictionary defines stress as ‘A state of mental or emotional strain or tension resulting from adverse or demanding circumstances’.
  2. The mental health foundation defines stress as ‘the degree to which you feel unable to cope as a result of pressures that are unmanageable’ [1].

Scientifically, stress is a biological response to a specific situation that triggers your flight or fight response by flooding the body with chemicals and hormones.

Individuals react differently to a situation; what is stressful for one person, another may find enjoyable such as presenting to large audiences. Almost any event can cause stress, but unexpected money problems, death of a loved one and divorce are among the top ten causes of stress according to a recent survey on British citizens [2]. In some cases, mental health conditions, genetic makeup and previous life experience can make some people more easily stressed than others [3].


The biology behind stress

When a stressor occurs, our brains release the Adrenocorticotropic hormone (ACTH) into the blood stream, where it travels down our body to the adrenal glands, found on the tops of our kidneys. ACTH causes the adrenal glands to flood our blood with the stress hormones cortisol and adrenaline where they act upon other organs and bodily systems to prepare for a fight or flight scenario. This biological reaction to stress can cause changes in a person in three different ways; bodily, emotionally, and behaviourally.

In the body, stress will result in a cascade of changes in the nervous, cardiovascular, hormone, and immune systems. Less essential functions such as digestion and the production of growth and sex hormones are suspended [3]. Simply put, during times of threat, eating and sex is NOT important! This means the body can focus on breathing, blood flow, alertness, and the preparation of muscles for activity as part of the all-important fight or flight response. Energy is made readily available by your liver, and faster breathing rates means an increase in oxygen intake. A rise in our blood pressure and heart rate further ensure that these tissues receive the energy and oxygen as rapidly as possible [4].

Physical symptoms of stress include an increase in your pulse and breathing rates as your body attempts to get more oxygen to the muscles to use for sudden activity. You will get pains in your muscles due to general muscle tensing, and you will feel less tired due to a heightened state of alertness. Once the stressor has been overcome, the levels of adrenaline and cortisol decreases, and bodily functions return to normal.

Emotional reactions can include anger, burnout, fatigue, forgetfulness, restlessness, and irritability [5]. Stress will also result in behavioural changes in individuals, particularly those that are unaware of their stress or simply don’t know how to cope. Changes in eating behaviours (eating more or less than usual), sudden angry outbursts, alcohol and drug misuse, and social withdrawal can all be associated with stress.


The good, the bad, the ugly: The different types of stress

The National Institute of Mental Health (NIMH) recognises two different types of stress: Eustress, which is positive stress, and distress, which includes chronic and acute stress [6]. Eustress is the most common form of stress and results in short lived changes to stress hormone levels inside the body. It is thought to be necessary for healthy development, teaching the brain how to respond to stress in a healthy way. Examples of Eustress could include stress involved in a promotion or starting a new job.

Acute stress is the common form of distress, usually triggered by pressures a person finds negatively stressful, such as a breakup or the loss of a member of family or friend. Acute stress can become harmful over extended and repeated periods of time; it is then termed chronic.
Triggers of chronic stress can include ongoing family or marital problems and poverty, or traumatic experiences [3]. These stressors can’t immediately be resolved, and those effected by them often stop seeking solutions, and hormones associated with the flight or fight pathway struggle to return to a normal level in a person experiencing chronic stress.


Long term effects of chronic stress

Chronic stress can lead to some serious health issues. For example, the constant increased blood pressure and heart rate can lead to permanent damage of veins and arteries, along with an increase in blood cholesterol levels. This can result in serious diseases and issues, such as coronary heart disease, atherosclerosis, heart failure and strokes [8, 9]. People who suffer with chronic stress also have a weakened immune system and are more susceptible to common colds and flus than people who are not suffering from stress [10, 11]. Some other major health issues related to stress can include memory disorders, problems with the reproductive systems, psychological diseases (such as PTSD), cellular ageing and mood disorders.


Final remarks

Everything in this article so far seems bleak. However, identifying stress and your triggers for stress can reduce the chances of it ever becoming chronic. Luckily, there are also ways of coping and recovering from stress. For example, exercise has been shown to reduce the memory impairment of stress in mice. Other little things to manage stress include breathing and relaxing using meditation techniques, reduction of recreational drugs and time planning and management. In some cases, talking to a therapist can greatly help identify the key stressor in your life and doctors can prescribe medications for the mental side effects of stress, such as depression or anxiety. It is also important to remember there are ways we can help the people around us who are suffering from stress, simply by listening to them and offering advice and support. If you are at all worried by the way stress could be affecting you mentally or physically, it is always recommended to reach out to close family and friends, doctors, and therapists.



  1. Mental Health foundation. Stress. March 26, 2021
  2. The Physiological Society. Stress in modern Britain
  3. Dialogues in Clinical Neuroscience, 2006. Genetics of stress response and stress-related disorders. 8(4), pp.433-444.
  4. Schneiderman, N., Ironson, G. and Siegel, S., 2005. Stress and Health: Psychological, Behavioral, and Biological Determinants. Annual Review of Clinical Psychology, 1(1), pp.607-628.
  5. National Health Service. Stress. Oct 15, 2019.
  6. MentalHealthHelp. Types of Stressors
  7. E. Scott. What Is Chronic Stress? Very Well Mind: Dec 07, 2020
  8. Dimsdale, J., 2002. Psychological stress and cardiovascular disease. BMJ, 325(7360), pp.393a-393.
  9. Steptoe, A., Kivimäki, M., 2012., Stress and cardiovascular disease. Nat Rev Cardiol 9, 360–370
  10. F. S. Dhabhar. Enhancing versus Suppressive Effects of Stress on Immune Function: Implications for Immunoprotection and Immunopathology. NeuroImmunoModulation 16(5).
  11. Cohen, S., Tyrrell, D. and Smith, A., 1991. Psychological Stress and Susceptibility to the Common Cold. New England Journal of Medicine, 325(9), pp.606-612.
  12. Ahola, K., Sirén, I., Kivimäki, M., Ripatti, S., Aromaa, A., Lönnqvist, J. and Hovatta, I., 2012. Work-Related Exhaustion and Telomere Length: A Population-Based Study. PLoS ONE, 7(7), p.e40186.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.