Can you really train your vagus nerve to calm down?

Humming, gargling, ice baths, cold water on the face: social media is full of "vagus nerve hacks" promising an instant reset for anxiety and stress. The vagus nerve is real, and its role in calming the body is real too. But the specific claims made for many of these techniques run well ahead of the evidence.

What the vagus nerve does

The vagus nerve is the main channel of the parasympathetic nervous system, the branch that slows the heart, aids digestion and helps the body settle after a stress response. One of its clearest, best-documented jobs shows up in the "diving reflex": when the face meets cold water, signals travel via the trigeminal nerve to the brainstem, which sends a vagal signal that slows the heart down, an evolved way of conserving oxygen underwater (Godek & Freeman, 2022). What is far less established is that triggering this reflex, or humming, or gargling, produces a lasting change in anxiety or resilience, rather than a brief dip in heart rate in the moment.

Where the evidence is strong

The best-tested technique in this space is one of the least dramatic. A randomised controlled trial of 108 adults compared several breathing exercises against mindfulness meditation over a month. One technique stood out: cyclic sighing, a double inhale through the nose followed by a long exhale through the mouth, sometimes nicknamed the "physiological sigh". Five minutes a day produced the largest gains in mood and the biggest drop in resting breathing rate of any group tested, meditation included, with the effect growing stronger the longer people practised (Balban et al., 2023). Alongside this, a 2022 meta-analysis pooling 223 studies found that slow, paced breathing more generally reliably raises vagally-mediated heart rate variability, a marker of parasympathetic activity, both during the practice and for some time after (Laborde et al., 2022). Breathing, tested properly and repeatedly, holds up. Many of the more viral techniques have not been tested anywhere near as thoroughly.

Why "vagal tone" gets overclaimed

Much of the popular content in this space draws on polyvagal theory, an influential framework that treats a single measure of vagal activity as a general marker of emotional resilience and social safety. A detailed 2023 critique in Biological Psychology examined the theory's core premises against cardiac and respiratory physiology and found several of them unsupported or contradicted by the evidence (Grossman, 2023). None of this makes the vagus nerve unimportant. It is a caution against treating "vagal tone" as one dial you can turn with a breathing app or a cold shower and expect broad, lasting change in how resilient you feel.

The bigger picture

Stress and anxiety sit at the crossing point of the physical, the psychological and the social. A slower heart rate in the moment can genuinely help you feel calmer and think more clearly, in a stressful meeting or a difficult conversation, which matters for how you show up with other people, not just how you feel alone. But five minutes of breathing is not a substitute for addressing what is actually driving chronic stress: workload, relationships, sleep, money. Framing a breathing technique as a fix for all of that is where the overclaiming creeps in.

Try these evidence-based techniques

1. Try cyclic sighing: two inhales through the nose, then one long, slow exhale through the mouth, for five minutes. It has the strongest single-technique evidence behind it so far (Balban et al., 2023).

2. More broadly, slowing your breathing rate for a few minutes, with a longer exhale than inhale, is one of the more robust calming techniques available (Laborde et al., 2022).

3. Treat cold water on the face as a real but short-lived effect, useful for taking the edge off an acute spike, not a long-term fix for anxiety (Godek & Freeman, 2022).

4. Be wary of any claim that a single "vagus nerve hack" will reset your nervous system for the day. The evidence favours repeated, ordinary practice over one dramatic intervention.

5. If anxiety is frequent, intense or affecting daily life, that is a reason to speak to your GP or a qualified therapist, not something to manage with breathing techniques alone.

A calmer nervous system may be closer than you think, just a few mindful breaths away.

References:

Balban, M. Y., Neri, E., Kogon, M. M., Weed, L., Nouriani, B., Jo, B., Holl, G., Zeitzer, J. M., Spiegel, D., & Huberman, A. D. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 4(1), Article 100895. 

Godek, D., & Freeman, A. M. (2022, September 26). Physiology, diving reflex. In StatPearls. StatPearls Publishing. 

Grossman, P. (2023). Fundamental challenges and likely refutations of the five basic premises of the polyvagal theory. Biological Psychology, 180, Article 108589. 

Laborde, S., Allen, M. S., Borges, U., Dosseville, F., Hosang, T. C., Iskra, M., Mosley, E., Salvotti, C., Spolverato, L., Zammit, N., & Javelle, F. (2022). Effects of voluntary slow breathing on heart rate and heart rate variability: A systematic review and a meta-analysis. Neuroscience & Biobehavioral Reviews, 138, Article 104711.