Many people nowadays are troubled by stress in their day to day lives. In this article, we discuss what stress is and how stress actually works.
Definition of stress
Stress has many definitions. One of the early definitions are as follows:
Stress is the non-specific response of the body to any demand.
Another, more detailed definition is as follows:
Stress is the subjective state of sensing potentially adverse changes in the environment that will lead to a response that enables the animal to adapt to the changing environment.
This demand that causes stress, i.e. the adverse changes in the environment, may be caused by stressful life events or stressors, such as an upcoming exam, a job interview, getting stuck in traffic, a financial crisis, a personal life crisis and so on. The stressors can be either external events (such as death of a family member or a job interview) or internal.
Stress is, therefore, an adaptive process with the following steps:
- The adverse changes in the environment are perceived by the brain regions, leading to release of stress mediator molecules to deal with the changes
- This triggers the stress responses in the person, including physiological, cognitive and behavioral responses, that enable the person to adapt to the stressful changes in the environment
Short-term stress
Stress can be useful in the short term. It is useful for functioning and survival, since it helps the body to be alert and deal with the immediate issue that needs attention. It helps the person to get an improved performance in terms of memory, alertness and other faculties.
For example, if we have an important work deadline or exam coming up, stress helps to focus the blood flow to focus on the brain and this helps us to think more clearly.
So in evolution, stress helped us to survive better by dealing with the imminent threat immediately.
Biological mechanisms of stress
The biological mechanisms of stress function in such a way that energy of the body and the blood gets diverted to the brain when the stressor (adverse change in environment) occurs, at the cost of longer term and less urgent mechanisms such as digestion, so that the person is better able to deal with the immediate threat or task. The body responds to stress in a dynamic and adaptive way, such as via increased heart rate and faster breathing and other appropriate changes. The result is that the stable function of the body is maintained.
The biological mechanisms of adaptation include things such as activation of the HPA axis (hypothalamic–pituitary–adrenal axis). This involves the activation of the region of the brain called hypothalamus, which then activates the pituitary glands and then affects the adrenal cortex activating the adrenal glands. The adrenal gland releases the hormone cortisol in the blood. This causes changes in the sympathetic nervous system, which governs the fight or flight response, causing changes such as pupil dilation, conversion of glycogen to glucose, secretion of adrenaline and noradrenaline, reduces the bladder constriction and digestive system, increases heart rate etc. It also causes changes in the immune system, cardiovascular system affecting blood pressure, and related changes, in such a way that one is better equipped to deal with the stressor. This normal adaptive response is termed as allostasis. Input from the amygdala region of the brain that deals with emotions is also involved in the HPA axis activation.
Chronic or long-term stress
In the long term, in modern day life, most of our stress is not caused by a sudden danger or threat. It is more of a continued low intensity stress such as fear of losing our job or financial troubles. This causes long term or chronic stress.
When we are under chronic stress, the benefits such as increased alertness that we get from short term stress no longer holds true. Repeated, prolonged or chronic stress can reduce the effectiveness of the normal allostatic response of the body It can weaken our immune system, cause health conditions such as diabetes and significantly weaken our standard of life. It impacts our wellbeing and our cognitive performance.
This detrimental cumulative effect of chronic stress is termed as allostatic load.
A good overview of how stress works can be found in the following book:
Sapolsky, R. M. (2004). Why zebras don’t get ulcers: The acclaimed guide to stress, stress-related diseases, and coping. Holt paperbacks.
Reviews and summaries of the book can be found here and here.
Mindfulness for stress reduction
Mindfulness, or mindful meditation, such as the ones taught in structured programs like MBSR or mindfulness based stress reduction, can help to reduce the stress.
Mindfulness involves exercises such as sitting in a meditation posture (back erect, cross legged, closed eyes, hands on lap) and paying attention to the breath as it comes in an goes out through the nostrils. One pays gentle and sustained focused attention on the breath. If the mind wanders, such as a thought occurs or an itch or pain sensation occurs, one acknowledges the sensation, notes it (one can use a neutral word such as pain, pain or thinking, thinking) and gently returns to noting the breath. One does not need to go deeper into the sensations, but if any movement is needed to get rid of something like pain in the leg, that is done also very slowly and mindfully.
The mechanism how mindfulness can help reduce stress is by training us to note our body sensations as they occur and thus increase our awareness of the stress response. It also trains us to accept our thoughts and feelings as they occur, without judging them as desirable or not.
The beneficial effects of mindfulness on stress have been studied widely. Mindfulness helps to enhance the immune system and other mechanisms. Biological markers of stress such as the cortisol levels in saliva and blood, blood pressure, heart rate variability, cytokine levels, and so on have been measured in various studies and found to be improved in case of practitioners who have done the MBSR course, compared with control groups without MBSR.
Some important books and articles by Jon Kabat Zinn explaining MBSR are as follows:
Kabat-Zinn, J. (1994). Wherever you go, there you are: Mindfulness meditation in everyday life. New York: Hyperion.
Kabat-Zinn, J. (2013). Full catastrophe living, revised edition: how to cope with stress, pain and illness using mindfulness meditation. Hachette UK.
Kabat-Zinn, J. (2013). Some reflections on the origins of MBSR, skillful means, and the trouble with maps. Mindfulness (pp. 281–306). Routledge.
A good review of the effects of MBSR on biomarkers is given in the following article:
Reive, C. (2019). The biological measurements of mindfulness-based stress reduction: a systematic review. Explore, 15(4), 295–307. doi: 10.1016/j.explore.2019.01.001 https://www.sciencedirect.com/science/article/abs/pii/S1550830718302842
One can also search for MBSR related studies and effects on various biomarkers on google scholar or Pubmed.
Conclusion
In this article, we have briefly discussed some of the mechanisms of stress and how mindfulness can help to reduce stress.
