This article was medically reviewed by Dr. Troy Noonan, MD Psychiatry. Dr. Noonan received his M.D. from Finch University at the Chicago Medical School, Psychiatry Residency and fellowship at the University of South Florida (USF) College of Medicine. He is Certified by the American Board of Psychiatry & Neurology.
How Much Does Stress Affect Your Immune System?
Just how much does stress affect your immune system? If you’re asking this question, you’re not alone. There’s a lot written on the link between stress and illness, but a lot of misleading claims as well. This article will cut through the common fictions and fake statistics about stress and explain how it affects your biological systems, including your immune system.
As you know stress is unavoidable, but not all stress has a negative effect. The term *Eustress (coined by Hans Selye, founder of “The Stress Theory”) is used to refer to positive stress.
*The prefix of this word is derived from the Greek word for “well.”
Positive stress is stress that motivates us to grow, adapt, and to overcome physical, mental, or emotional challenges. For example, physical exercise puts your body under temporary stress, but it also makes you physically stronger. A healthy amount of stress can give you the competitive motivation to do your best and to push your limits.
Excessive exposure to stress, however, can have negative effects on your physical and mental health. It can wear down your biological systems and cause a variety of complicated problems, many of which we’ve talked about in our articles on Anxiety Disorders, Depression, PTSD, and other mental health challenges.
Harmful stress is called distress, or (in more technical language) chronic stress. Chronic stress can stunt physical healing and cause cognitive problems like poor memory, lack of concentration, and performance anxiety.
It can severely limit your ability to use the physical or cognitive skills and talents you’ve developed. More importantly, chronic stress can literally turn your immune system into a weapon that attacks your healthy tissues. Over time, chronic stress can cause complicated diseases that are often blamed on other causes, and therefore inadequately treated.
This article will give you a better understanding of the link between stress and illness (mental, and physical alike). Let’s start by looking at the difference between ordinary stress, and distress, and how good stress can turn into bad stress.
How Your Immune System Responds to Stress
Stress can be classified as physical, mental, or emotional. However, each of these types of stress can take a physical toll on your body. This is especially true if you’re experiencing all three at the same time (more on this in a moment).
Inflammation is the first key to understanding how stress physically affects your body. In layperson’s terms, inflammation is how your immune system protects your body from infection or from (further) physical injury. It does this in response to a temporary infection or injury, and it’s completely normal and healthy. Think about the last time you got an insect bite, a twisted ankle, a burn, a broken limb, or a soft tissue injury. That puffy redness and irritation around the wounded area is inflammation.
This swelling and irritation last only until the injury has healed—then it goes away. This is called acute inflammation. Acute inflammation is your immune system protecting the injured tissue long enough for it to heal. Inflammation also happens inside your body—in your muscles, your vital organs, and even in your heart and brain. This happens because your immune system uses inflammation to fight off viruses, parasites, bacteria, fungi, and other damaging invaders.
When inflammation is working properly, your immune system sends biological agents (enzymes, white blood cells, antibodies, etc.) to fight off infections.
Once the inflammation has served its purpose, your immune system returns to normal functioning. However, when inflammation becomes out of control, your immune system remains in attack mode.
In this case, it can literally lay siege to your healthy tissues just as it would to an infection-causing agent.
This is called chronic inflammation, and it’s one of the most common causes of physical disease. Unlike acute inflammation, chronic inflammation is not short-lived, nor healthy. Think of chronic inflammation as the dark side or the evil twin of your immune system response. It causes your otherwise normal and beneficial immune response to become a liability to your physical and mental health.
Chronic Stress, Inflammation, and Physical Disease
I explain the difference between Acute Stress and Chronic Stress in our article on the link between stress and depression. To quote that article, acute stress is like your body pulling the fire alarm, while chronic stress is your body acting as if the fire never stopped burning. This is when stress becomes a problem.
The 2017 journal Frontiers in Human Neuroscience published a study concluding that inflammation is a “common pathway” for stress-related diseases. While the authors of the study weren’t clear on how direct this connection is, we do know that chronic stress and chronic inflammation often go together. We also know that being in a chronic state of stress makes it harder for your body to heal and to recover. It can also intensify and prolong the symptoms of common infections.
For example, when an infection enters your body, your immune system dispatches chemicals to the affected area to neutralize the infection. These chemicals seep into tissues around the infected area.
This can include your organs, muscles, or connective tissues. This is how inflammation causes flu-like (headaches, tiredness, chills, fever, stiffness, and loss of appetite) in response to infections.
If the exposure to these chemicals continues, it can damage your organs, joints, and other tissues. For example, a persistent case of gout, a reactionary form of arthritis, can cause permanent joint damage. This is the long-term impact of chronic inflammation. Inflammation damage is associated with autoimmune disorders and chronic and deadly diseases.
For example, inflammation in the heart (Myocarditis) can cause chest pain, irregular heartbeat (arrhythmias), fluid buildup, swelling in legs, ankles or feet, fatigue, and shortness of breath. Inflammation in the lungs (one of the more severe symptoms of COVID-19) can cause severe shortness of breath and painful or labored breathing. In the liver and kidneys, inflammation can have a severe effect on your body’s ability to flush toxins and to absorb nutrients.
These symptoms of liver inflammation can be mild or life threatening. In the kidneys, inflammation can cause high blood pressure and kidney disease. Since your liver and kidneys are pivotal to ridding your body of toxins, inflammation in these organs can affect your ability to fight off disease and to flush toxins. This can lead to chronic toxicity and a multitude of systemic health problems.
Stress and Inflammation in The Vital Organs
In the brain, inflammation is called encephalitis. Brain inflammation can cause mild flu-like symptoms, but it can also cause seizures, confusion, problems with movement, or problems with the senses of sight or hearing. Encephalitis can also be life-threatening, and cause emotional and mental health problems, which we’ll talk about in the next section.
All of these are examples of a perfectly natural immune response becoming dangerous to the health tissues of your body. Living in a chronic state of stress puts your body in a state of biological panic that causes your immune system to attack its own tissues. A familiar example of this is how COVID-19 becomes deadly. During my research for this article, I found a 2021 article on the University of California San Francisco website that featured quotes from multiple medical professionals on how your immune system can cause COVID-19 to become deadly.
This is just a glimpse of how chronic stress and inflammation can make your body more susceptible to disease by weakening your body’s ability to fight off disease. Picture your body as an empty bucket with three water faucets over it.
One of these faucets represents emotional stress, the second represents illness (infection, toxins, etc.), and the third represents physical stress (injury, pain, etc.).
If you turn the physical stress faucet, your bucket will fill up slowly. If you turn two faucets on, it will fill up faster. Turn all three on, and it will fill up and overflow faster than your immune system can stop it. This overflow represents your body becoming overwhelmed by disease. Imagine having two of these faucets (physical and emotional stress) always running.
Even if you appear reasonably healthy, a sudden infection or illness can cause a sudden overflow of complicated health problems. Your immune system is designed to keep the water in your bucket at a safe level, but it can also become part of the problem. This is a metaphor for the relationship between chronic stress, inflammation, and your immune system’s ability to protect you from disease.
Although not always cited as the cause, chronic inflammation is linked to many health problems, some of which include diabetes, asthma, cancer, heart disease, arthritis (rheumatoid arthritis, fibromyalgia, psoriatic, osteoarthritis, lupus, gout, etc.), and Alzheimer’s disease. This is why stress management skills can be valuable and essential for protecting your long-term health, and this goes beyond your physical health.
Chronic Stress, Inflammation, and Your Mental Health
Mental health researchers have learned a lot over the past ten years about the relationship between inflammation and our mental and emotional health. For example, patients with depression and/or anxiety benefit from anti-inflammatory medications (i.e., aspirin and ibuprofen).
"Aspirin can reduce oxidative stress and protect against oxidative damage. Early evidence suggests there are beneficial effects of aspirin in preclinical and clinical studies in mood disorders and schizophrenia, and epidemiological data suggests that high-dose aspirin is associated with a reduced risk of AD. Aspirin, one of the oldest agents in medicine, is a potential new therapy for a range of neuropsychiatric disorders, and may provide proof-of-principle support for the role of inflammation and O&NS in the pathophysiology of this diverse group of disorders."
Inflammation and Neurotransmitters
The most striking connection between inflammation and mental health lies in the effect of inflammation on two major neurotransmitters, dopamine and serotonin.
These two neurotransmitters play a key role in clinical depression, and it’s treatment. Recent findings have also suggested that brain inflammation can affect neuronal circuitry.
"“Some of the mechanisms that might be responsible for inflammation-mediated sickness and depression have now been elucidated. These findings suggest that the brain–cytokine system, which is in essence a diffuse system, is the unsuspected conductor of the ensemble of neuronal circuits and neurotransmitters that organize physiological and pathological behavior.”
Cytokines, mentioned in the above quote and again below, are small proteins produced in almost every cell of your body. The combination of pro- and anti-inflammatory cytokines are necessary for regulating your immune response. However, pro-inflammatory cytokines can activate immune cells and can cause the release of more cytokines. The term “cytokine storm” was coined to describe a sudden burst that causes excessive inflammation.
Proinflammatory cytokines can have a negative effect on the key neurotransmitters mentioned above. When it comes to your mental health, serotonin (aka, “The happy hormone”) is one of the most important of these neurotransmitters. Proinflammatory cytokines can inhibit serotonin production by depleting a protein essential to serotonin production:
““Data indicate that cytokines and their signaling pathways including p38 mitogen-activated protein kinase have significant effects on the metabolism of multiple neurotransmitters such as serotonin, dopamine, and glutamate through impact on their synthesis, release, and reuptake. Cytokines also activate the kynurenine pathway, which not only depletes tryptophan, the primary amino acid precursor of serotonin, but also generates neuroactive metabolites that can significantly influence the regulation of dopamine and glutamate.”
Some researchers believe that the Serotonin Reuptake Inhibitors SSRI and SNRI (both of which are a popularly prescribed antidepressants) may be more effective because of their anti-inflammatory properties more than their inhibition of neurotransmitter reuptake (Source: A comparative examination of the anti-inflammatory effects of SSRI and SNRI antidepressants on LPS stimulated microglia).
The impact of inflammation on your immune system and your mental health doesn’t stop with your brain. More than ninety percent of your serotonin is produced in your gut. Likewise, seventy to eighty percent of your immune cells are in your gut.
"“About 95% of 5-HT is estimated to be found in the gut mainly within the enterochromaffin cells whereas about 5% is found in the brain.” "
This makes well-balanced gut bacteria essential to maintaining good immune health, and healthy serotonin levels. Dysbiosis (the term used to describe gut microbiome imbalance) often alters the expression of the genes that regulate inflammation, causing gut inflammation.
Even low-grade gut inflammation can make the intestinal linings more permeable, causing “leaky gut syndrome.” Reduction in good gut microbes also leaves room for harmful microbes, such as E. coli and B. fragilis.
Bad gut bacteria can cause inflammatory responses and make it harder for your body to break down and absorb nutrients from food. When bad microbes die, they release proinflammatory molecules called endotoxins, which can also cause inflammatory responses.
“Several studies suggested that alterations in the gut-microbiota may contribute to a modulation of serotonin signaling.” “Serotonin plays a key role in the regulation of visceral pain, secretion, and initiation of the peristaltic reflex; however, its altered levels are also detected in many different psychiatric disorders. Symptoms of some gastrointestinal functional disorders may be due to deregulation in central nervous system activity, dysregulation at the peripheral level (intestine), or a combination of both (brain-gut axis) by means of neuro-endocrine-immune stimuli.”
Serotonin plays an important role in mood regulation, digestion, sleep cycles, and nervous system performance. Considering this, it’s easy to see why low levels of serotonin are associated with clinical depression, anxiety disorders like PTSD, and Obsessive Compulsive Disorder (OCD). In 2017, Canadian researchers compared twenty OCD patients to a twenty person control group who didn’t have the condition. The researchers found that inflammation thirty-two percent six brain regions that play a role in OCD.
""Our research showed a strong relationship between brain inflammation and OCD, particularly in the parts of the brain known to function differently in OCD. This finding represents one of the biggest breakthroughs in understanding the biology of OCD, and may lead to the development of new treatments."
Treating Stress Related Problems Without Medication
Thankfully, the FDA has approved a safe, effective, and reliable way to treat Clinical Depression, and OCD using Transcranial Magnetic Stimulation (TMS). Transcranial Magnetic Stimulation was approved by the FDA in 2008 as a valid option for treating depression without medication. It was also FDA approved in 2018 for treating obsessive-compulsive disorder (OCD).
If this is your first time hearing about this treatment option, you’ll find more information about TMS in our articles on treating depression without medication, and our comparison of TMS vs ECT therapy, and our article on TMS therapy and PTSD.
Our mental health articles give you the data on why TMS is the safest and most effective method for treating clinical depression and other mental illnesses mentioned here. If you’re ready to take positive action toward better mental health, start by contacting us today, or taking one of the mental health assessments on the Mental Health Management website.
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