What is the vagus nerve – and why should you care?

Photo adapted from Steven Lasry from Unsplash

She’s everyone’s favourite nerve. She’s the celebrity of nerves, the one that most people have heard of, possibly the only nerve they can name. Some have tried to dethrone her, claiming that she isn’t all the world says she is; that the phrenic nerve is more important, more interesting. But, at least in the yoga world, the vagus nerve is queen.

I’m not very good with celebrity gossip. Even with biological celebrities, like the vagus nerve, I feel I came a bit late to the party. It was the summer of 2015, the summer of my mid-life crisis/career break/Science Communication MSc, and I was interning as my dream role: news reporter at New Scientist. My co-intern was a psychologist, much younger than me of course. She was telling me about a device that stimulates the vagus nerve to treat depression (I have no memory of why were talking about it, and she never seems to have written about it either, so who knows).

I was fascinated – an electrical device that treats depression? A single nerve with the power to do all of that?

(of course, at that point I hadn’t realised that I already knew about the vagus nerve because I knew about the gut–brain axis, I just had no idea that there was a single nerve in charge of that and that the vagus nerve was that.).

But enough about me.

So, what is the vagus nerve?

I love the alternative name for it – “wanderer nerve” (so much so, I wrote a poem about it). It really tells the story of the nerve that travels the whole distance from the brain all the way to gut, passing a huge range of tissues and organs along the way: the throat, the heart, the stomach, the gut, among others.

At any given time, the vagus nerve sends signals to the brain and back to each and every tissue and organ it passes, to make sure that everything is ok and to respond appropriately when needed. In a previous post I compared it to the matchbox string phones we used as kids, where each organ can have a direct line of communication to the brain, and vice versa. [Try and find an image of that, by the way. When you search for phones these days, you only get mobiles. I feel like a dinosaur]

Why would you need a direct line of communication?

Think of what happens when you burn yourself in scalding water – you immediately retract your hand. A signal goes from your skin to your brain and back to the muscles of your fingers to get you to move your hands. That’s not the vagus nerve of course, but hopefully it gives an idea of why the brain needs to communicate with everywhere else in the body.

But what does it actually do?

The vagus nerve does a ton of stuff, such as regulating our appetite and our immune system. Basically, anything to do with bringing back balance to each and every tissue and organ it passes.

But the reason those of us in the wellbeing world care about it (and the reason that it’s queen) is that it’s the main nerve of the parasympathetic nervous system – what is sometimes referred to as “rest and digest”, the partner (or rival?) to the sympathetic, or “fight or flight” response.*

it’s the main nerve of the parasympathetic nervous system – what is sometimes referred to as “rest and digest”

What this means is that when the vagus nerve is activated, it balances out the effects of stress (and heightened sympathetic activation) on the body.

Physical stress (for example, an infection, not enough sleep, actual hardship) and emotional stress (what we normally think of as stress) trigger what is known as the HPA axis – our central stress response system. This ultimately leads to changes in the body that help us deal with the stressor, like an increase in the stress hormone cortisol and increased inflammation.

Activation of the vagus nerve brings this back to balance. And balance is what we want. **

Back to yoga – where does the vagus nerve fit in?

When I first registered the vagus nerve, it was in the context of an electrical device that stimulated it to treat depression.

The beauty of yoga is that there is evidence that it can also stimulate the vagus nerve. Not only that, but it can also support the vagus nerve in working more effectively, improving what is known as vagal tone (a fancy way of saying how well it works to balance out the effects of the stress response).

Slowing down the breath (either directly or indirectly, as might naturally happen during a gentle yoga practice or meditation) has a magical calming effect when we are feeling stressed, and this is through the activation of the vagus nerve.

This stimulation of the vagus nerve explains a lot of the beneficial effects of yoga on our health

This stimulation of the vagus nerve explains a lot of the beneficial effects of yoga, including breathing practices and meditation, on our health, including:

Autoimmune diseases, like Crohn’s disease and rheumatoid arthritis

These are diseases of excessive activation of the immune system, so activation of the vagus nerve (through yoga or otherwise) reduces inflammation and alleviates symptoms. There is a growing body of literature on the beneficial effects of yoga in this context (eg. here).

Depression and anxiety

Again, possibly due to the inflammation link, although there are likely to be other reasons too.

Heart disease

I’m not sure there is direct research on this but we know that yoga helps to tackle stress via the vagus nerve, that yoga has beneficial effects in heart disease, and that the vagus nerve passes through the heart and controls things like heart rate.

There’s probably more but this post is getting longer than the blogging gods allow, so I better wrap up.

So, does she deserve the queen title?

I’m sure there are tons of other exciting nerves doing all sorts of exciting things. But there is surely something very special about a nerve that connects all the things I care about – immunology, yoga and mental health/psychology. So for me, she is definitely a winner.

What do you think?


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*Now, I know that sometimes this simplistic explanation of the two arms of the autonomic nervous system is controversial. But from a science communication perspective, it’s the easiest way to explain it. So if this offends you, sorry. I’m lazy, what can I say.

**Of course in the yoga world we have a tendency to adore parasympathetic activation and vilify the sympathetic nervous system. But balance is what we want. Too much parasympathetic and you’re lethargic or asleep. Too much sympathetic and you are jumping around like the Energiser bunny.

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