The Parasympathetic Nervous System, Vagus Nerve, and Stress Relief

By Dr. Douglas Cowan, Psy.D., MFT

Take a slow, deep breath right now. Exhale longer than you inhaled. Notice what happens in your body.

That shift — the slight settling, the softening of the shoulders, the subtle slowing of the heart — is your parasympathetic nervous system engaging. It happens in seconds. It is always available to you. And most people with anxiety have no idea it exists, let alone how to activate it deliberately.

The nervous system has two modes. Most of us have heard of one — the fight-or-flight response, the sympathetic branch that mobilizes the body under perceived threat. What gets far less attention is the other — the parasympathetic branch, the rest-and-restore mode that is the body's natural counterbalance to stress. When the parasympathetic system is working well, you can handle pressure and come back to baseline. When it's working poorly — when the sympathetic stays dominant and the parasympathetic can't engage — that's chronic anxiety.

At the center of the parasympathetic system is a structure that most people have never thought about but that may be the most important nerve in the body for mental health: the vagus nerve.

What's Happening in the Brain

The autonomic nervous system — the part of the nervous system that runs bodily functions below the level of conscious awareness — has two primary divisions. The sympathetic division accelerates: it raises heart rate, dilates the pupils, increases respiration, releases cortisol and adrenaline, and mobilizes the body for action. The parasympathetic division decelerates: it slows the heart rate, promotes digestion, lowers inflammation, and restores the body to a balanced state after stress.

In a well-regulated nervous system, these two systems work in balance — the sympathetic activates when genuine threat requires it, and the parasympathetic re-engages once the threat has passed. In chronic anxiety, this balance is broken. The sympathetic system dominates, the parasympathetic system can't fully engage, and the body lives in a state of chronic low-level emergency.

The vagus nerve is the primary carrier of the parasympathetic system. It is the longest cranial nerve in the body, running from the brainstem through the neck and down into the heart, lungs, and digestive organs — touching nearly every major system. Roughly 80 percent of the signals it carries travel upward: from the body to the brain. This means the vagus nerve is not primarily a command line telling the body what to do — it is primarily a reporting line, carrying information from the body's organs to the brain's regulatory centers.

This is why what the body does affects the brain's state so directly. Change the breathing pattern, and the vagus nerve carries that change to the brain. Change the posture, or activate the vocal cords through humming, or immerse the face in cold water — each of these changes the signals the vagus nerve sends upward, and the brain's emotional centers respond.

Vagal tone — the health and responsiveness of the vagus nerve — is measured through heart rate variability (HRV): the natural variation in time between heartbeats. High HRV indicates a flexible, responsive autonomic nervous system that can shift appropriately between sympathetic and parasympathetic states. Low HRV indicates a rigid, stuck system — often chronically sympathetically dominant. Chronic anxiety is associated with low HRV. Practices that improve vagal tone improve HRV, and improving HRV is associated with reduced anxiety, better emotional regulation, and improved cognitive function.

Stephen Porges, a neuroscientist at Indiana University, developed a framework called Polyvagal Theory that clarifies why this matters so much. He describes three states of the autonomic nervous system: the ventral vagal state (associated with calm, safety, social engagement, and connection), the sympathetic state (fight-or-flight mobilization), and the dorsal vagal state (shutdown, freeze, dissociation). Healing and genuine learning only occur in the ventral vagal state. Anxiety lives in the sympathetic and dorsal vagal states. The path back to regulation runs through the vagus nerve.

Now You Understand Why

When you understand the vagus nerve's role, the experience of anxiety takes on a different meaning.

The anxious person is not weak. Their nervous system is not broken. Their parasympathetic system has lost the ability to adequately counterbalance the sympathetic — often because of chronic stress, trauma history, poor sleep, sedentary lifestyle, or social isolation, any of which can reduce vagal tone over time. The system that is supposed to bring them back to baseline cannot gain traction.

The good news in this is significant: vagal tone can be improved. The nervous system is plastic. The pathways that carry calming signals can be strengthened with practice, just like any other physiological system. The practices that improve vagal tone are not complicated or expensive. They are accessible to virtually anyone.

Why does the exhale calm you faster than the inhale? Because the exhale specifically activates the vagus nerve. The inhale slightly accelerates heart rate; the exhale slows it. A longer exhale than inhale shifts the autonomic balance toward parasympathetic dominance within seconds. You have a built-in calming mechanism that requires nothing but air and the willingness to use it.

Why does humming help? Because the vagus nerve runs directly through the vocal cords. Vibrating the vocal cords — through humming, singing, chanting, or gargling — sends vibrations directly into the vagal pathway, activating the parasympathetic response from the inside out.

Why does safe social connection calm anxiety? Because the ventral vagal system is specifically associated with social engagement. The face, voice, and eye contact of a safe, regulated person co-regulates a dysregulated nervous system. This is not metaphorical — it is neurological. Human connection is a vagal nerve intervention.

What Wisdom Looks Like Here

The practical wisdom here is to build vagal tone systematically — not just to use these techniques in moments of crisis, but to make them daily practices that gradually shift the baseline.

Signs that your parasympathetic system is struggling include: chronic anxiety or hypervigilance that doesn't seem tied to any particular situation; digestive issues (IBS, nausea, bloating — the gut is heavily innervated by the vagus nerve); persistent sleep problems; brain fog or chronic fatigue; difficulty feeling genuinely calm or present even when circumstances are relatively stable.

If several of these are present, a dedicated vagal tone practice is worth treating as seriously as any other health intervention.

What To Do Starting Today

• Practice extended-exhale breathing every day. The most reliable vagal activation technique available. Breathe in for four counts, hold for two, exhale for six to eight counts. Do this for five minutes in the morning before the day's demands begin. Over weeks, this practice measurably improves HRV and lowers resting anxiety levels. In acute anxiety moments, even three cycles of this pattern begins to shift the autonomic state.

• Hum deliberately for two minutes daily. Sustained low-frequency humming — with the mouth closed, feeling the vibration in the throat and chest — directly stimulates the vagus nerve. It is simple, quiet (you can do it while driving or doing dishes), and genuinely effective. Many contemplative traditions across cultures independently discovered this and built it into prayer and spiritual practice long before neuroscience explained why it works.

• Seek safe connection as a biological intervention, not just a social preference. When you are anxious, the face and voice of a calm, caring person is a neurological treatment. A phone call with a trusted friend, sitting with someone who is genuinely regulated — these are not just emotionally helpful. They are activating your ventral vagal system. Isolation, particularly chronic isolation, reduces vagal tone. Connection restores it.

• Use cold water for acute regulation. Splashing cold water on the face or holding cold water against the cheeks activates the diving reflex — a hard-wired mammalian response that immediately slows the heart rate and shifts the autonomic balance toward parasympathetic dominance. This works in seconds and requires nothing more than a sink.

• Pray and meditate with slow, deliberate breath. Research on prayer and meditation consistently shows improvement in HRV, reduced cortisol, and increased parasympathetic tone. The mechanism is partly the breath (these practices inherently slow breathing), partly the attentional shift from threat to gratitude or surrender, and partly what people of faith understand as something the data cannot fully capture. However it works, it works — and it has for as long as anyone has written down what they tried when life got too hard.

• Consider CES for direct nervous system regulation. Cranial Electrotherapy Stimulation works through a mechanism that parallels vagal stimulation — shifting the autonomic system toward parasympathetic dominance through low-level electrical current, with research showing improvements in HRV and anxiety reduction. For people whose vagal tone is very low and who find it difficult to engage other regulation practices, CES can be a helpful starting point that creates enough physiological ground to build on.

• Move your body every day. Aerobic exercise is one of the most powerful vagal tone interventions available. Regular moderate exercise consistently improves HRV, reduces resting cortisol, and strengthens the parasympathetic system's ability to engage. Twenty to thirty minutes of brisk walking produces measurable effects.

The body always knows the way back to calm. That is not naive optimism — it is physiology. The vagus nerve is your nervous system's reset button. It has been there since birth, waiting for you to learn how to use it.

Start with the breath. The breath is always there. The rest follows.

References

1. Porges, S. W. (2011). The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, and Self-Regulation. Norton.
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3. Capilupi, M. J., et al. (2020). Vagus nerve stimulation and the cardiovascular system. Cold Spring Harbor Perspectives in Medicine, 10(2), a034173.
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