Author: Jonine Moller
Stress is something that we all become accustomed to quite early in life. As a child, we may experience stress when we have to do a speech in class. The pressure to perform in sport is also a common source of stress for children and athletes. As we grow older, we learn about financial stress and stress about the future and its accompanying uncertainties.
Stress is a term used so widely, but do we truly understand it? In attempts to explain stress, we might use words such as worry or anxiety. When we start to think about it, though, we might wonder whether the meaning goes deeper.
Firstly, stress can be categorized as either acute or chronic. Likewise, stressors can be either acute or chronic . Acute stress reactions are (usually) necessary and adaptive responses with positive effects. Chronic stress is more often “bad” and detrimental to your health .
To understand the physiological reaction of stress, we will run through the physical responses to stressors. A stressor is anything that the body experiences as a threat of any kind. Acutely, the physical effects are the same for all types of “threats” perceived. The purpose of the response is to prepare your body to deal with the threat .
Physically dealing with a threat involves being able to either fight or flee. The sympathetic nervous system (SNS) is activated when you are exposed to an acute stressor. The SNS is the fight or flight response branch of the autonomic nervous system.
With the activation of the SNS, the adrenal glands (on top of the kidneys) produce and release catecholamines. These are the hormones responsible for the physical effects of stress - adrenaline and noradrenaline. Dopamine is another catecholamine, but more on this hormone later.
The physical manifestations of the SNS activation are increased heart rate and breathing [2, 3]. The hormones involved also signal the liver to release glucose as a quick energy source [2, 3].
The SNS hormones released and their effects are to give us a physical boost. This boost in what allows us to function at a higher level for a better chance of survival. This type of stress reaction is, of course, beneficial for sports performance as well.
Together with the adrenal glands, the hypothalamic-pituitary-adrenocortical (HPA) axis stands central to controlling the body’s stress response. The result of the HPA axis activation is increased cortisol levels .
Cortisol is a glucocorticoid and probably the most famous stress hormone. The adrenocorticotropic hormone, released by the pituitary gland, tells the adrenal glands to release cortisol.
The pituitary gland is, in turn, stimulated by an increase of a hormone released by the hypothalamus. All happens secondary to the activation of the HPA axis [2, 3, 4].
Cortisol promotes the breakdown of fat and protein and the production of glucose. This increases energy availability. Cortisol also exerts regulatory effects on the cardiovascular, metabolic, and immune systems . Short term, cortisol improves the efficacy of the systems for the fight and flight response .
Chronic release of the hormone cortisol, in response to stress, has adverse effects on health. Long-term increased levels suppress the production of certain immune cells. As a result, it hinders the functioning of the immune system . The functioning of the cardiovascular, metabolic, and nervous systems is also negatively affected .
A chronic high level of cortisol can lead to weight gain. It can also lead to the following health risk factors and symptoms that are closely related to insulin resistance :
- Increased blood lipids and cholesterol - Increased blood sugar - High blood pressure - Abdominal obesity
It is established that there are individual differences in the physiological responses to stress. The amount of cortisol secreted and heart rate increases differ, for example .
The effect that different stressors have on the body is very much dependent on the individual . Several gene variations have been associated with a greater increase in blood pressure in response to stress .
Variations of the COMT gene are involved in the HPA axis reactivity. This partly explains why the reactivity of the HPA axis differs among different people . With cortisol being the primary end-product of the HPA axis, differences in HPA activity will influence the amount of cortisol released .
The specific COMT gene variation mentioned above is also famous for determining whether you are prone to have a warrior or worrier personality . In other words, variations within the COMT gene determine, to a degree, what effect stress has on your mental performance. The COMT enzyme plays a crucial role in the regulation of dopamine [8, 9]. The prefrontal cortex of the brain releases dopamine. This hormone plays a part in the regulation of behavior and mental processes .
Higher activity of the COMT enzyme causes more breakdown of catecholamines (including dopamine). Less of these hormones will thus be found in the blood resulting in weaker activation of the prefrontal neurons. Lower COMT activity has the opposite effect .
People with higher COMT activity have worse performance with memory and attention tasks. People with lower COMT activity are, however, more sensitive to pain . Stress may improve the mental performance of individuals with higher COMT activity. However, the extra dopamine release due to stress may be less advantageous in the case of low COMT activity [4, 8].
Higher COMT activity allows for better functioning under stressful situations. These individuals are said to have the “warrior” personality. Individuals with lower COMT activity typically don’t cope as well with stress and are, therefore, “worriers” . Worriers may be at higher risk for suffering from anxiety disorders [4, 10].
As with all genetic traits, many factors (genetic and environmental) play a role and influence each other to determine the phenotypic outcome. We always need to keep this in mind.
Of note, perception of stressful situations or tasks may not reflect the degree of the physiological stress reaction. Researchers found this when they compared physiological measures of the stress response to stress perceptions .
Have your genes tested today to understand better how your body responds to stress and how to deal with it. Knowing your physiological make-up is crucial to understanding your stress response. Understanding your physiology is key for being empowered and in control of yourself. Head over to our traits toolkit so you can take charge by first learning about yourself.
 Iob, E., & Steptoe, A. (2019). Cardiovascular Disease and Hair Cortisol: a Novel Biomarker of Chronic Stress. Current Cardiology Reports, 21(10). https://doi.org/10.1007/s11886-019-1208-7
 Kemeny, M. E. (2003). The Psychobiology of Stress. Current Directions in Psychological Science, 12(4), 124–129. https://doi.org/10.1111/1467-8721.01246
 Lee, D. Y., Kim, E., & Choi, M. H. (2015). Technical and clinical aspects of cortisol as a biochemical marker of chronic stress. BMB Reports, 48(4), 209–216. https://doi.org/10.5483/BMBRep.2015.48.4.275
 Armbruster, D., Mueller, A., Strobel, A., Lesch, K. P., Brocke, B., & Kirschbaum, C. (2012). Children under stress-COMT genotype and stressful life events predict cortisol increase in an acute social stress paradigm. International Journal of Neuropsychopharmacology, 15(9), 1229–1239. https://doi.org/10.1017/S1461145711001763
 Bibbey, A., Carroll, D., Roseboom, T. J., Phillips, A. C., & de Rooij, S. R. (2013). Personality and physiological reactions to acute psychological stress. International Journal of Psychophysiology, 90(1), 28–36. https://doi.org/10.1016/j.ijpsycho.2012.10.018
 Herd, J. A. (1991). Cardiovascular response to stress. Physiological Reviews, 71(1), 305–330. https://doi.org/10.1152/physrev.19220.127.116.115
 Rimpelä, J. M., Niiranen, T., Jula, A., Pörsti, I. H., Tikkakoski, A., Havulinna, A., Lehtimäki, T., Salomaa, V., Kontula, K. K., & Hiltunen, T. P. (2019). Genome-wide association study of white-coat effect in hypertensive patients. Blood Pressure, 28(4), 239–249. https://doi.org/10.1080/08037051.2019.1604066
 Stein, D. J., Newman, T. K., Savitz, J., & Ramesar, R. (2006). Warriors versus worriers: The role of COMT gene variants. CNS Spectrums, 11(10), 745–748. https://doi.org/10.1017/S1092852900014863
 Stein, M. B., Fallin, M. D., Schork, N. J., & Gelernter, J. (2005). COMT polymorphisms and anxiety-related personality traits. Neuropsychopharmacology, 30(11), 2092–2102. https://doi.org/10.1038/sj.npp.1300787
 Hoth, K. F., Paul, R. H., Williams, L. M., Dobson-Stone, C., Todd, E., Schofield, P. R., Gunstad, J., Cohen, R. A., & Gordon, E. (2006). Associations between the COMT Val/Met polymorphism, early life stress, and personality among healthy adults. Neuropsychiatric Disease and Treatment, 2(2), 219–225. https://doi.org/10.2147/nedt.2006.2.2.219