When we’re stressed out, our body’s internal chemistry changes. Cortisol, the primary stress hormone alongside adrenaline and norepinephrine, surges. As a result, blood sugar levels increase and more of that glucose is allocated to the brain.
That’s good — the chain reaction helps our bodies in the so-called “fight-or-flight” response, which has a deep evolutionary history and dwells within us even today. When potential predators were around, our ancient ancestors needed that extra boost to figure out whether to take them on or run away. Nowadays, the same biochemical responses spring into action to help us react quickly when we’re under pressure.
The Harmful Effects of Chronic Stress
Our bodies, however, no longer only trigger the fight-or-flight response when we’re seriously threatened. The same processes are triggered when we’re late for work or arguing with family members. And after dealing with a pandemic for over a year, many more Americans are becoming acquainted with prolonged psychological stress, according to the American Psychological Association's poll, Stress in America 2023: A Nation Recovering from Collective Trauma. Often times, our response to this stress can be more harmful than helpful.
“We know that the immune system is capable of looking at these proteins and reacting,” says Willem van Eden, an immunologist at Utrecht University in the Netherlands. Protracted exposure to higher levels of stress hormones comes along with myriad side effects within the immune system.
Largely speaking, stress can be divided into two camps: the psychological and the physical, also known as physicochemical stress. While psychological stress is caused by worrying about something (whether it’s a predator or a looming deadline), physical stress comes from environmental factors such as air pollution, poor nutrition or exhaustion.
Chronic psychological stress has been linked to a subdued immune system. But if the immune system becomes compromised and is no longer capable of dealing with physical stresses, this can promote the onset of disease.
Read More: The Biology of Stress in Your Body
How Stress Weakens the Immune System
Scientists first noticed a link between stress and the strength of immune systems during animal experiments in the early 1980s. The experiments quickly progressed to humans when researchers began observing medical students. They found that students’ immunity dropped around exam time with depleted levels of T-cells, some of the immune system’s most important weapons in the fight against infection.
Additional studies showed that chronic stress interferes with the molecular signals that immune cells use to communicate with each other. More recently, Scott Mueller, a professor at the University of Melbourne in Australia, demonstrated that stress can even stop immune cells from moving, physically blocking them from thwarting infections and cancers.
In a 2021 mouse-based study, Mueller and his colleagues used a special microscope — able to observe biological processes within living organisms — to create real-time images of a chemical messenger protein called noradrenaline. The protein is found in higher concentrations under stressful conditions and obstructs the movement of various white blood cells that are important in the immune response. This “explains at least in part the widely observed relationship between stress and impaired immunity,” Mueller concludes in the study.
Read More: 5 Facts You Might Not Have Known About Anxiety and How to Treat It
The Link Between Stress and Cancer
Another study, published in Frontiers in Immunology in 2018, demonstrated the impact of stress on the immune system by inducing stress and cancerous tumor growth in mice — some of whom were additionally given an antidepressant. The results showed a marked difference: The mice treated with antidepressants had significantly reduced cancer progression compared to those who weren’t.
While it’s possible that the antidepressants themselves possess cancer-fighting mechanisms, the researchers concluded that the inhibition of psychological distress (thanks to the antidepressant) is likely what restored antitumor immunity.
Cancer isn’t the only disease that seems to progress more rapidly under stressed environments. Research has shown that chronic stress also increases a person’s risk of heart disease, weight gain, digestive issues, headaches, muscle pain and, of course, mental health problems such as anxiety and depression.
In short, our immune systems are at their best when we’re not beset with high levels of cortisol pumping through our veins.
Read More: Why Do I Get Sick So Often, While Others Stay in Freakishly Good Health?
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Indian journal of endocrinology and metabolism. Stress and hormones
Harvard.edu. Understanding the stress response
American Psychological Association. Stress in America 2023: A nation recovering from collective trauma
Reuters. Air pollution ups stress hormones, alters metabolism
Frontiers in Immunology. Editorial: Stress and Immunity
American Psychological Association. Stress effects on the body
Frontiers in Immunology. Beneficial Effect of Fluoxetine and Sertraline on Chronic Stress-Induced Tumor Growth and Cell Dissemination in a Mouse Model of Lymphoma: Crucial Role of Antitumor Immunity
Chronic Stress. Neurobiological and Systemic Effects of Chronic Stress
Benjamin has more than a decade of experience reporting on science in the Middle East, covering subjects such as the rebuilding of Mosul University in Iraq after its liberation from Islamic State. He is now based in London where he likes to write about the life and medical sciences. His work has been published by Associated Press, Chemical & Engineering News, Nature, Scientific American, and Wired Magazine. He has a bachelor's degree from Imperial College, London and a master's degree in journalism from New York University.
