Chronic Stress

Chronic Stress

For most people chronic stress has become a regular aspect of modern life, amplified by a bombardment with negative news from the internet: the pandemic, catastrophic climate events, political polarization, and a raging war in the middle of Europe are just the most recent examples. As I will explain, our biology is poorly equipped to deal with this type of constant and repeated exposure to stress 24 hours a day. The mismatch between our ancient biological acute stress response systems and this new form of chronic perturbation of the body’s homeostasis is likely to negatively affect our health.

Acute, often life-threatening stress has been part of human life for millions of years and there has been enough time in our evolutionary history to perfect our biological stress response systems in a way that has kept our species alive through natural disasters, wars, famines, and pandemics. There are two such systems in our body: the older immune stress response system and the brain’s stress response system, and both are often engaged together.

Our organism responds to any situation – in the presence or the future – that is perceived as a threat to our integrity and homeostasis by engaging one or both of these stress response systems. While they have evolved and are optimized to respond to infrequent, but life-threatening stresses – the poisonous snake, the wild tiger, the severe injury, or the infection, for most people in developed countries, these are no longer the kind of stresses we encounter on a regular basis. Unfortunately, the worry about being shot remains a persistent stress for a significant segment of the population as highlighted by the series of recent high profile police shootings.

Today’s perturbation of our body’s balance most often comes in form of chronic stressors associated with modern life: The chronic psychological stress on our minds generated by the relentless daily bombardment with negative news, worries about the future, increasing competition, and number of challenges associated with a lower socioeconomic status (in plain language, poverty, food insecurity, health conditions). And at the same time, the dietary stress on our metabolism in form of the unhealthy Standard American Diet (SAD).

Unfortunately, these two types of stressors often occur together, and the relentless engagement of our stress systems comes at an increasing cost to the health of our bodies and minds. Evolution had not foreseen these kinds of stressors which we have never experienced as a species. While our stress response systems (the sympathetic nervous system and the HPA axis) keep responding in the same way that has been so adaptive for human life, chronic hyperproduction of the stress mediator’s cortisol and noradrenaline, and chronic systemic engagement of the immune system are responsible for many aspects of our current chronic non-infectious disease epidemic as I have described in detail in The Gut Immune Connection.

Not everybody responds to these challenges in the same way: the responsiveness of our neurological and immunological stress system is influenced by genetic factors and is programmed during the first 18 years of life, starting in utero, and will determine our lifetime risks for developing these common chronic diseases. This will result in a situation where two people exposed to the same kind and severity of stress will respond in very different ways: one will remain healthy, the other one developing a chronic disease.

In this short videoclip, I provide a brief explanation of the relentless transition that has been occurring in the US and increasingly in developing countries from a state of optimal health and the associated subjective feeling of wellness to the current epidemic of chronic non-infectious diseases and provide an understanding of how both psychosocial and dietary stresses interact to result in a maladaptive engagement of the stress systems ultimately leading to organ dysfunction and disease.

If you want to learn more about this topic, you might also be interested in my book, The Gut Immune Connection, which is available now.


Dr. Emeran Mayer is a Distinguished Research Professor in the Departments of Medicine, Physiology and Psychiatry at the David Geffen School of Medicine at UCLA and the Executive Director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience at UCLA.