How stress messes up your immune system (and where yoga fits in)

Photo by George Pagan III on Unsplash

Starting this post by saying that stress is bad for us feels like quite the pointless introduction, almost like writing a school essay. But yes, stress is bad for us. And we all know that. Stress can have a negative effect on our health, driving the development of cardiovascular disease, metabolic disease and even cancer.

And stress is bad for our immune system too.

Here’s a simple example. You’ve had a really tight deadline at work. You’re working long hours every day, with non-stop pressure from your boss/colleagues/clients. As soon as the project finishes, you get sick. Sound familiar?

The mind (and brain) and body are really closely connected; how we feel will affect how our body feels too, including how well our immune system can work. So when we are stressed, especially for prolonged periods of time, it really has an impact.

Stress affects our immune response

There are two types of stress. Acute stress is the kind of stress you experience short-term, for instance having an argument with a friend or your partner or jumping out of a plane with a parachute (yes, that was apparently a real experiment). Chronic stress is stress that you experience long-term, for instance if you are constantly arguing with your partner, work become relentless or even toxic, or your living conditions become unbearable (ie living in a building site for 6 months, like I am at the moment, sigh).

Acute stress activates the inflammatory response

In essence, acute stress mimics what happens when we get an infection – our brain sends a signal to our immune system to alert of the potential threat. Our body then switches on the expression of the genes that code for molecules to promote inflammation. (remember, inflammation refers to the recruitment of immune system cells to a part of the body that needs help, eg to deal with the attack from a virus or bacterium).

Within a very short space of time, our immune cells are mobilised and ready for action. If you jump out of a plane with a parachute, apparently that will increase the activity and numbers of some immune cell types.

Chronic stress is a bit more confusing

Ok, so this is where things get a bit complicated. Maybe the simplest way to understand this is that chronic stress messes up the immune system in various different ways.

In some instances, it seems to suppress the immune system so that it’s not strong enough (and that’s why you might get sick after a prolonged time of stress at work or at home). In others, chronic stress leads to chronic inflammation, which means unregulated immune responses that cause damage to our tissues and organs, and leads to chronic diseases like heart disease and diabetes.

chronic stress messes up the immune system in various different ways

Chronic stress also means we have high levels of cortisol and other corticosteroids – these are hormones that put brakes on the immune response. Under normal circumstances, this is a good thing; it’s a way for the body to regulate itself so that it can keep inflammation under control and off when no longer needed. But because chronic stress is constant and relentless, our bodies get used to the cortisol and stop responding to it. And now our immune response is basically out of control.

There is some explanation of how you can get different outcomes here, but it seems to relate to how stress affects different components of the immune system, which do different things. The other explanation is that stress is just too generic a term, so different types of chronic stress may affect the body in different ways. Yes, it’s all very complicated.

Where does yoga fit in?

Many (if not all) of the beneficial effects of yoga on the immune system lie on its effects on stress.

Yoga activates the vagus nerve

Ok let’s be clear first. There has long been a tendency in the yoga world to overemphasize the importance of the parasympathetic nervous system (also called the ‘rest and digest’ system) and vilify the sympathetic nervous system (or ‘fight or flight’). But if we just did things to activate our parasympethic nervous system all the time, then we would just be asleep or at the very least lethargic all the time. Remember, it’s all about balance.

Yoga practices, in particular breathing practices, have been shown to activate the vagus nerve – this is the major parasympathetic nerve that acts as a line of communication between the brain and most organ systems in the body (see here for more on the vagus nerve). But this doesn’t mean it makes you fall asleep, just that it bring the system back to balance.

Yoga can also act indirectly

Another theory is that the beneficial effects of yoga are indirect – practicing yoga can influence other health behaviours, for example helping us sleep better. This would then influences our stress response and lead to that same outcome of balance.

Has yoga helped you manage your stress levels?

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