What does stress do to the immune system?

Do you find yourself with a cold or major health issue after a stressful event? I most certainly do.

I’m constantly full of anxiety trying to do everything, and it’s not just all of the lists, and kids, and home maintenance, and work, and writing these articles (which I love doing); it’s a personality trait, and it’s quite common.

All of these little things in our lives add up and cause us STRESS.

So, what’s stress?

We can define it as a state of mental tension and worry caused by problems in our lives.

When you feel stressed your body releases chemicals in response to stress hormones circulating through the body. Sometimes these hormones can be useful, however often they are very hard on the body and can leave you susceptible to infection.

When is stress useful?

You’ve most likely heard of the ‘fight or flight’ response–a survival alarm system dated way back to the beginning of human life. This response occurs in the face of real danger and causes the hypothalamus to stimulate the adrenal glands to start pumping adrenaline. This gives your body the energy to either fight or flee from a dangerous situation. We still use this response today in the face of say, encountering a bear on a hike or a mugger on the street.

Stress chemicals may also be useful before a big event when you may need a burst of energy or alertness to improve performance. This might be beneficial during a job interview or before a big test.

But, chronic stress is often harmful. 

Chronic (long-lasting) stress does no good and can knock down both mental and physical health. Constant worrying often leaves you vulnerable to many health issues.

One example of chronic stress is Post-Traumatic Stress Disorder (PTSD), which can occur after a traumatic event. This may leave the sufferer to be stuck in the ‘fight-or-flight’ response, causing a constant release of stress hormones, and consequently a vast array of health problems and infections.

What happens in the body during times of stress?

When stressed, the body produces the stress hormone called cortisol. This hormone prepares the body for the ‘fight-or-flight’ response. When it does this it suppresses the immune system by lowering the amounts of chemicals needed to signal immune cells, which means a lowered number of T cells and B cells needed to fight infection. This leaves the body with an increased risk of infection and may leave the body fighting longer to fend off infection.

What are the effects on the immune system from stress?

The immune system is a collection of billions of cells that travel through the bloodstream.  They move in and out of tissues and organs, defending the body against foreign bodies (antigens), such as bacteria, viruses, and cancerous cells.

In stressful times, the brain sends defense signals to the endocrine system, which releases hormones normally released in emergency situations. These stress hormones severely depress the immune system.

The hormone corticosteroid suppresses the effectiveness of the immune system by lowering the number of lymphocytes (white blood cells) circulating the body. The flooding of cortisol not only decreases white blood cells, but also natural killer cells (cells that kill cancer and virus-infected cells) leading to increased tumor development and growth, as well as increased rate of infection and tissue damage. This leaves the body unable to control inflammation and infection, therefore the immune system is compromised.

Glaser et al. investigated the effect of a stressful event on the immune system. They took blood from 75 first-year medical student volunteers at a month before their final examinations (low stress) and then during the examinations (high stress). The immune function was assessed by measuring the T cell activity in the blood. The students were also given a questionnaire to assess life events and psychological variables, which also play a roll in stress levels.

This team found that that the blood taken during the time of low stress had more T cells compared to the blood taken during times of high stress, concluding that stress lowers T cell count in the blood. This means lowered immune function in the body.

What are the effects of stress on the body?

Stress chemicals cause chronic inflammation in the body, potentially harming tissues and organs, leading to major health problems. In fact, stress may be responsible for as much as 90% of illness and disease such as cancer and heart disease.(3)

Much of the body’s immune system function is found in the gut, therefore with stress, the gastrointestinal system suffers, and can leave the body with health problems such as chronic disease and allergies. After a stressful event, digestive activity increases due to adrenaline and in turn may lead to gastric ulcers.

The adrenaline from the ‘fight-or-flight’ response also puts the heart into overdrive, causing it to beat and circulate blood faster than normal causing high blood pressure and risk of heart disease such as hypertension (raised blood pressure). High blood pressure can create lesions on artery walls.(2)

Adrenaline can also increase blood cholesterol levels through the release of free fatty acids. This leads to a clumping together of cholesterol particles that can create clots in the blood and artery walls.

And because the heart is pumping more rapidly during times of stress, there may be a more rapid build-up of cholesterol on artery walls that are now lesioned due to high blood pressure.

Chronic stress and the high rate of the ‘Fight-or-flight’ on the body affects nearly all body systems, including your mental functioning. Chronic stress can increase the risk of anxiety, depression, and problems sleeping. This may lead to unhealthy coping behaviors such as excessive alcohol/drug use, smoking, risk-taking, to name a few.

How do you overcome stress and have balance back in your body?

The effects of stress are cumulative and can lead to serious health issues, but there are ways to reverse the stress.

Exercise is a simple and effective way to reduce stress. It doesn’t matter what you do, just get your body moving. Doing this benefits your adrenal glands, and stress hormones will divert to helping you move your body instead of destroying your tissues.

Probiotics may help increase the immune function in your gut, which is the center of your immune system. Taking measures to eat healthier is also a great way to boost the health of your immune function.

Deep breathing exercises may help calm the body by reducing the ‘fight-or-flight’ response. Practice this in times of stress. It will cause the hypothalamus to return to rest mode and will lower your heart rate. Meditation and relaxation exercises should be a part of everyday life if you are a high-stress person.

Embrace the power of positive thinking. And talk it out! Get some social support. What are you stressed about? Getting to the root of the problem with a professional might be what you need to help banish some of the stress in your life.

You’ve heard that phrase, “stress kills,” right? Well, it might be true. Take precautions today so you aren’t in trouble tomorrow!

Wishing you the best!



1.”Stress, Illness, and the Immune System” in Simply Psychology. Written by Saul McLeod (2010).

2. “Holmes and Rahe Stress Scale” resources at Science Direct.

3. Segerstrom, Suzanne C., and Gregory E. Miller. “Psychological Stress and the Human Immune System: A Meta-Analytic Study of 30 Years of Inquiry.” Psychological Bulletin 130.4 (2004): 601–630. PMC. Web. 28 Dec. 2017.

4. Glaser, et. al. “Stress-related impairments in cell-mediated immunity.” Psychiatry Research. 16.3 (1985): 233-239.

5. Andrew Golszek, Ph. D. “How Stress Affects the Immune System. Psychology Today. WEB

6. Suzanne C. Segerstrom and Gregory E. Miller. “Psychological Stress and the Human Immunes System: A Meta-Analytic Study of 30 Years of Inquiry.” Psychological Bulletin. 130.4 (2004): 601-630. PMC. Web. 7 Feb. 2006.