How Stress Affects Your Immune System

stress affects immune system

Have you ever noticed how some people just seem to never get sick? Maybe you know someone like this. While everyone around them coughs and sneezes through the winter, they somehow manage to come out on the other end without so much as a sniffle, year after year.

If you’ve encountered one of these cold-and-flu-proof people, you might be wondering what their secret is. Why do some manage to pick up every nasty bug that comes their way while others coast through life on what appears to be a wave of superhuman immunity?

While there is no set-in-stone formula for keeping every person healthy in every situation (and sometimes it simply comes down to plain, old-fashioned good luck), there are a few things you can do to boost your chances of being one of those aforementioned superhumans. There is a strong link between stress and the immune system, so a big thin you can do is this: get a handle on your stress!

Why Controlling Stress Matters

The complex “Team Immunity” is made up of cells in your blood, skin, bone marrow, tissues, and a variety of organs that – when all is humming along as it should – protect our bodies against potentially harmful infectious critters such as viruses and bacteria while mitigating the cellular damage caused by noninfectious agents such as sunburn, according to the National Institutes of Health (NIH). Much like Goldilocks, we want an immune system that is neither under- nor over-reactive, but just right.

While I could write for days by digging into the aforementioned details of immunology (and I have written a lot about how to boost your immune system here already), here we will focus on the aspect of immunity that is both nearest and dearest to my heart and what I consider to be the cornerstone of good health and the immune system’s MVP: the gut.

Is Stress Always Bad?

Although “stress” as a general concept has gotten a very bad rap, it’s important to recognize that short-term (i.e. acute) stress is a normal and healthy biological response to a stressor, be it psychological, physiological, or physical (including exercise).

key intersection of mind, body, and microbiome and a perfect example of the interconnectedness of our parts and systems, our body’s reaction to a stressor involves the release of hormones such as cortisol and adrenaline with instantaneous effects on multiple body systems, including cardiovascular, digestive, and immune (with some evidence suggesting that acute stress can actually be immunoprotective; for example, by enhancing wound healing and fighting or preventing infection, both of which can be very useful on the battlefield).

In other words, our short-term stress response is a kind of emergency system that has one job, which is to get us out of dangerous situations alive and intact.

Fight-or-Flight vs. Rest and Digest

Imagine this: you’re a Paleolithic teenager on your very first hunt when around the corner comes a ticked-off rival tribesman wielding a very sharp spear. What do you do? Certainly, you do not have time to weigh all of your choices. Instead, chances are you do one of two things, as if on autopilot: you fight back like there’s no tomorrow or you attempt to sprint safely away.

This short-term (“fight-or-flight”) stress response, lasting a few minutes to a few hours, is essentially Mother Nature’s survival mechanism and works by greatly enhancing our performance under conditions involving threat.

When challenged in this way, here is what happens within your body: your energy expenditure increases, while digestion is suppressed. Heart rate and cardiac muscle contractility increase. Blood pressure goes up. GI motility decreases while blood flow to your muscles increases. Reproductive ability goes kaput. In a nutshell, all nonessential functions are simply switched off so that we can focus on the matter at hand: survival. And for this finely orchestrated chain of events, we have our sympathetic nervous system (SNS) to thank.

@Gerald Oswald - Pixabay

By preparing our body for intense physical activity in response to a stressor, this built-in survival mechanism, which still serves us well today, has been of exceptional benefit from an evolutionary perspective and is technically the reason we are all here; after all, those who were successful at fighting or running away had the best chances of procreating.

Once the threat is gone, however – for example, when you either get away or manage to kill the rival tribesman before he kills you – your sympathetic nervous system calms down again and you will no longer be in fight-or-flight mode.

Cue the activation of the parasympathetic nervous system (PNS). Also known as “rest and digest” mode, the PNS can be thought of as functioning in direct opposition to the SNS. When the PNS is activated, your heart rate slows and your gut motility perks back up. Your ability to conserve energy increases. You start feeling amorous again and your full immune system comes back online. And instead of making you feel anxious and wigged-out (like the SNS does), it produces a calm and relaxed feeling in both your mind and your body.

So, while the sympathetic nervous system activates your body’s response to threats, the parasympathetic activates its response to safety and security. Or, put another way, the SNS is your body’s gas pedal and the PNS, its brakes.

How does this all play out in modern life, though? Therein lies the problem.

Indeed, most of us live in a chronic state of SNS over-activation. In other words, faced with non-stop stressors from our extremely busy and fast-paced modern lives, our sympathetic nervous system can remain continuously activated, and it’s this chronic stress that can wreak havoc on our bodies.

What About Our Immune System?

As I mentioned before, in short spurts, stress hormones like cortisol can actually be immunoprotective. However, researchers have found that sustained, long-term stress has the opposite effect and can result in chronic infection, chronic inflammatory autoimmune diseases, or cancers as well as other physiological disorders. Chronic stress can all but obliterate your immunity. Fortunately, there are things you can do to directly counteract its effects.

So what should you do? Remove yourself from ongoing stress. While I know this might sound easier said than done, it might not be as difficult as you think.

Think about it this way: PNS activation is technically your body’s “baseline.” Your SNS exists to help you cope when something out of the ordinary happens, and when your SNS is activated, that means your PNS can’t be. But the opposite is also true; when your PNS is activated, your SNS will stay quiet and out of trouble. The key is to keep your parasympathetic nervous system – your “rest and digest” mode – activated for as much of the time as possible, and this is something you can largely control!

As Dr. Rick Hanson (The Neuroscience of Lasting Happiness) points out, “there is actually a neurological system in your body that you can trigger at will to help yourself feel less stressed, more peaceful, and more happy. Paying conscious attention to this system can, quite literally, override the effects of SNS hyper-stimulation and there are many ways of doing so.

While the usual suspects – meditation, massage, yoga, tai chi, deep breathing exercises, and long walks in nature (read more about exercise and the immune system here) – can be hugely impactful in achieving the rest-and-digest mode of PNS, just about anything requiring intense focus will help.

So if none of those appeal to you, don’t fret. Consider learning a new language, dusting off the musical instrument you haven’t played since high school, trying your hand at sudoku, or even coloring in one of those extremely detailed coloring books whose lines you can only see with a magnifying glass. The goal is to focus on something, anything, that will keep your mind off your usual feelings of overwhelm, tension, and worry.

Remember that every minute your body is experiencing rest-and-digest is just one more minute that it isn’t experiencing fight-or-flight and, in the long run, your immune system will thank you for it.

Separate to the reduction of stress, you could also look into immune system booster supplements using vitamins and nutrients proven to help improve your immune system’s response to illness. 


Bae, Y.-S., Shin, E.-C., Bae, Y.-S., & Van Eden, W. (2019). Editorial: Stress and immunity. Frontiers in Immunology, 10:245. doi: 10.3389/fimmu.2019.00245

Dhabhar, F. S. (2018). The short-term stress response: Mother nature’s mechanism for enhancing protection and performance under conditions of threat, challenge, and opportunity. Frontiers in neuroendocrinology, 49, 175-192.

Goldman, B. (2012). Stanford Medicine News Center. Study explains how stress can boost immune system. Accessed on June 20, 2020.

LeBouef, T., Yaker, Z., & Whited, L. (2020). Physiology, autonomic nervous system. StatPearls, National Institutes of Health. Accessed on June 19, 2020.

Loughman, A. (2016). Ancient stress response vs. modern life. Medium. Accessed on June 19, 2020.

Morey, J. N., Boggero, I. A., Scott, A. B., & Segerstrom, S. C. (2015). Current directions in stress and human immune function. Current Opinions in Psychology, 5, 13-17.

Segerstrom, S. C. & Miller, G. E. (2004). Psychological stress and the human immune system: A meta-analytic study of 30 years of inquiry. Psychological bulletin, 130(4), 601-630.

Wyss, J. M. (1993). The role of the sympathetic nervous system in hypertension. Current opinion in nephrology and hypertension, 2(2), 265-273.

Dr. Shari Youngblood
Latest posts by Dr. Shari Youngblood (see all)

Leave a Comment

Your email address will not be published. Required fields are marked *

John Riedl

Simply put that’s why I’ve gone down the health journey of research and creating health brands.

Our gallery
Scroll to Top