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Stress in depth - How deep does stress go?

Ask around, and you'll find that many people are "stressed" in life. From daily deadlines to nightly news, every aspect of society seems to be conspiring to inhibit the free and happy flow of life. What people are feeling is not just a mind thing. It's literally cellular. And it may not be all bad…

It's only in the movies that a person can calmly walk away from a traumatic event and get back to business as usual with a smile and a wave while the credits roll. In real life, most living organisms will have some sort of vigorous physical reaction to extreme stress situations. Even the most battle-hardened commandos know this, and they prepare for their combat missions accordingly.[1] 

The fight-or-flight response was first investigated and named by American physiologist Walter Cannon (1871-1945) in 1915. It involves a complex set of bodily functions that allow living beings to come to terms with stress. In brief, it works this way: Our senses, sight and hearing, keep watch of the environment and continuously send signals to a part of the brain called the amygdala, which normally handles emotion. When the amygdala perceives danger, it sends a message to the hypothalamus, which then calls for a release of epinephrine (adrenaline), which prepares the body for either fighting or fleeing. Heart and breathing rate as well as blood pressure increase and make sure muscles and vital organs are well supplied for the hard work on hand. The brain will also start producing cortisol as a way to sustain the defenses.[2]

Action and reaction

This superbly coordinated response is performed by the body's sympathetic nervous system, meaning it happens automatically and very fast. It is essential to the survival of living beings and is the result of millennia of evolution. Once the danger has passed, the parasympathetic nervous system ("feed and breed") kicks in to restore the body to its original state of attentiveness – which Cannon referred to as "homeostasis." The process can be accompanied by so-called neurogenic tremors, which are Nature's way of trying to get the body’s endocrine system back into balance. It can be observed in dogs that have just been fighting with another animal.

However, it would be wrong to think that once the event slips into the past that physical threats are the only events to which we react unconsciously or semi-consciously. Cannon himself was aware that psychological pressures were also capable of producing some response from the body. In the 1930s, one of his followers, a certain Hans Selye at McGill University in Montreal, explored the other factors that could impact people and animals. He was the first to use the word "stress" to "denote the stimuli that are capable of eliciting the alarm reaction," writes Dr. Istvàn Berczi from the Department of Immunology at the University of Manitoba. "These included physical, chemical agents and emotional factors."[3] 

The silent intruder

Today we know that stress has an enormous impact on our lives and quality of life.  And that stress comes from a wide range of sources. It can be individuals' use of drugs, tobacco, or alcohol. It can be the noise of a city, a nasty boss or colleague at work. It can even be societal situations. In 2019, the American Psychological Association (APA) conducted its Stress in America survey, which revealed, for example, that a major factor was fear of a mass shootings: "When asked which places they are stressed about the possibility of a mass shooting occurring, adults most commonly say a public event (53%), mall (50%), school or university (42%) or movie theater (38%), with only one in five (21%) saying they never experience stress as a result of the possibility of a mass shooting."[4]

This ubiquitous stress is a typical trigger for "long-term activation of the stress-response system and the overexposure to cortisol and other stress hormones that follow the body's response system, resulting in many health issues," according to the eminent Mayo Clinic,[5] including anxiety, depression, headaches, heart disease, sleep problems, weight gain and memory and concentration impairment.

Drilling down
The problem goes even deeper than just the body. A number of different studies have shown various ways in which stress can actually affect DNA. In 2011, a group of researchers at Duke University School of Medicine[6] published a seminal study suggesting that the constant flow of adrenaline produced by chronic stress is responsible for very real DNA damage. They conclude that "psychosocial stress in humans is not time-limited, because aspects of this type of stress response can be sustained over months or even years. This may lead to prolonged secretion of stress hormones and consequent adverse effects for the individual."

DNA can be affected in other ways as well, as research in epigenetics has shown. Translated into plain English, this field involves the study of how some chemicals, like the steroid hormones released during stressful situations, can actually alter the way genes "express" themselves, but without impacting the original genetic structure. The modification of DNA in the brain is known, but James Potash and Gary Wand of the John Hopkins School of Medicine[7] tried exposing mice to stress hormones by adding them to their water. This actually changed how the expression of the mice's genetic material in their response network (known as the HPA axis), and they started acting as if they were stressed even in stress-free situations.

The research, which is fairly new, suggests something quite disturbing. Continual stress of, say, work deadlines or noise, means that the regular fight-or-flight mechanism does not return the body to homeostasis. This, says Harrison Wein, science editor for the National Institute of Health, "can lead to depression or other mood disorders. Understanding the mechanism by which chronic stress leads to these conditions might help us find new ways to prevent or treat them in the future."[8]

The changing genes
Work on the environmental impact on DNA is painstaking, but progress is being made. Elissa Epel, a professor of psychiatry at the University of California, has been looking into the relationship between stress and DNA.[9] She examined the casing at the end of each strand of DNA known as telomeres, which tends to get depleted during cell division. The body does produce an enzyme called telomerase that helps restore it, but here's the problem: Cortisol produced from chronic stress tends to deplete the supply of telomerase, leading to the death of cells and aging. The type of stress determines the extent of the damage. "It seems exposures to multiple early life adversities, such as child neglect, have the largest effects," Epel said in an interview with the APA, "since they track through to late adulthood, or they set in place persistent mechanisms that maintain short telomeres throughout life, such as exaggerated stress reactivity and poor health behaviors."[10] 

There is no silver bullet that can counteract the impact of stress on our DNA, but Epel and others are unanimous in their belief that life style choices, exercise and attitude are excellent antidotes. Practicing mindfulness, for example, can help. According to the Harvard Medical School publication, physical activity can "stifle the buildup of stress. (…) Movement therapies such as such as Yoga, Tai Chi, and Qi Gong combine fluid movements with deep breathing..."[11] And, naturally, there is having close friends and family as support, particularly during stressful times. By the same token, not all stress is negative. Enjoying life and looking forward to fun events also causes the body to go through a hormonal transformation. But this time, the amygdala is not sounding the alarm, but rather saying "Rejoice!" loudly and clearly.

[1] Rocky Jedick. Combat Stress Response & Tactical Breathing. Go Flight Medicine. Posted April 10, 2019.

[2] Harvard Medical School. Understanding the stress response. March, 2011 (updated May 1)

[3] Istvàn Berzci. Hans Selye and the Birth of the Stress Concept. Brainimmune.com. Posted February 25, 2009.

[4] American Psychological Association. Health Care, Mass Shootings, 2020 Presidential Election Causing Americans Significant Stress, New Stress in America™ Survey Finds. www.apa.org. November 5, 2019

[5] Mayo Clinic Staff. Chronic stress puts your health at risk. Mayoclinic.org.

[6] Makoto R. Hara, Jeffrey J. Kovacs, Erin J. Whalen, et al.  A stress response pathway regulates DNA damage through β2-adrenoreceptors and β-arrestin-1. Nature. August 21, 2011.

[7] Harrison Wein. Stress Hormone Causes Epigenetic Changes. National Institutes of Health. September 27, 2010

[8] Harrison Wein. Ibid.

[9] American Psychological Association. How chronic stress is harming our DNA. Interview with Elissa Epel by Stacy Lu. October 2014, Vol 45, No. 9. Print version: p. 28

[10]American Psychological Association. Ibid.

[11] Harvard Medical School. Ibid.