The body doesn’t forget fear. But it can learn to feel safe.The Vagal System, Stress, and Relationships: The Hidden Biology of Well-Being.
In a big city, as night falls on the windows of skyscrapers and the streets remain lit like neural circuits, a woman checks into a hotel after a long journey. She has crossed an ocean, changed time zones, replied to messages, checked her documents, and held back her thoughts.
At the front desk, she smiles, but her body reveals a deeper truth: her shoulders are still tense, her breath is short, her stomach is knotted, and her heart is beating just a little faster than necessary.
Then something subtle happens. The person at the desk looks up, calls her by name, and speaks to her in a calm voice. There’s no rush. There’s no intrusiveness. There’s none of that automatic courtesy that often feels like a routine.
Instead, there is a composed presence. A simple gesture. A gentle steadiness. The woman inhales, almost without realizing it. Her body receives a signal even before her mind can formulate it: here, you don’t have to defend yourself. It is in that invisible transition—between alarm and trust, between tension and openness—that we can sense the silent work of the vagus nerve
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The vagus nerve is one of the major communication pathways in the human body. Its name derives from the Latin vagus, “wandering,” because it traverses the body like a deep-seated messenger: it originates in the brainstem and reaches vital regions, including the heart, lungs, and digestive system. It is not, as is often simplistically claimed, the “calm nerve,” which can, incidentally, be measured with specialized medical devices.
It is an essential component of the autonomic nervous system, involved in regulating vital functions such as heart rate, digestion, respiration, and physiological responses related to stress.
To speak of vagal functioning is to speak of safety as an embodied experience. Not merely a reassuring idea, not merely a psychological state, but a bodily state. The human body, in fact, does not always wait for reason to decide whether to open up or protect itself.
Before words, before analysis, before awareness, it registers signals: a tone of voice, a facial expression, a posture, a distance, a rhythm.
Safety has a grammar. And the body reads it.
In recent decades, this insight has been brought to the forefront of scientific and clinical debate, in part by Stephen W. Porges’s polyvagal theory. In his paper “Polyvagal Theory: A Science of Safety,” published in 2022 in Frontiers in Integrative Neuroscience, Porges proposes interpreting certain states of the autonomic nervous system in relation to the perception of threat, relational availability, and signals of safety.
An important clarification is needed, however. The polyvagal theory has had a major influence on trauma psychology, body-oriented psychotherapy, and popular science writing on the nervous system, but not all of its assumptions are considered definitively proven.
In 2023, Paul Grossman published a critique of the model’s main premises; in the same year, J. Sean Doody, Gordon Burghardt, and Vladimir Dinets challenged certain evolutionary assumptions related to sociality in vertebrates.
This caution does not weaken the argument. It makes it more serious. The point is not to turn the vagus nerve into a miracle formula for contemporary well-being. The point is to recognize that emotional life is not separate from the body.
What we call anxiety, trust, openness, closedness, presence, or fear flows through real biological circuits. The mind does not float above the organs: it inhabits them.
One of the windows through which research observes this complexity is the variability of heart rate, known as HRV, short for Heart Rate Variability. A healthy heart does not beat like a metronome. It varies, adapts, and responds.
Between heartbeats, there are microvariations influenced by breathing, the activity of the autonomic nervous system, stress , and many other physiological conditions. Fred Shaffer and J. P. Ginsberg have described HRV as the sum of the variations in the intervals between consecutive heartbeats; Paul Grossman and E. W. Taylor have emphasized the need to avoid simplistic interpretations of the relationship between respiratory sinus arrhythmia and cardiac vagal tone.
The neurovisceral integration model, developed by Julian F. Thayer and Richard D. Lane, has helped us understand the relationship between the heart and the brain as part of a broader network involved in emotional regulation, attention, and the body’s ability to respond to environmental demands.
The key word, then, is not calm. It is flexibility. A well-regulated body is not a body that is always calm. It is an organism capable of changing states. It activates in the face of a challenge, defends itself against a threat, slows down when the danger has passed, and becomes open to connection again when the environment allows it.
Health does not mean the absence of inner movement, but rather the ability to avoid being trapped in a single state.
Many people live as if their bodies were stuck in a state of alert. Even when everything seems to be going well, something remains tense. One sleeps, but does not truly rest. One speaks, but is ready to defend oneself. One listens, but anticipates the blow. In these cases, it is not necessarily a matter of fragility.
Often it is the biological memory of the threat: an organism that has learned to survive and struggles to believe that the danger is over.
Here, the relationship becomes central. From the very beginning of life, no human being regulates themselves alone. The newborn does not know the world through concepts, but through the body: the warmth, the heartbeat, the voice, the touch, the predictability of those who care for them. Before autonomy comes co-regulation. Before identity, there is a presence that helps the nervous system avoid being overwhelmed. This relational dimension is not merely poetic.
Scientific literature has long shown that the quality of social bonds is associated with health. A meta-analysis published in 2010 by Julianne Holt-Lunstad, Timothy B. Smith, and J. Bradley Layton, based on 148 studies and 308,849 participants, found that stronger social relationships were associated with a higher likelihood of long-term survival.
More recently, George M. Slavich proposed the Social Safety Theory, according to which developing and maintaining reliable social bonds represents a fundamental organizing principle of human behavior. From this perspective, isolation, rejection, exclusion, and persistent conflict can become powerful stressors, capable of interacting with neurobiological and immune processes.
Chronic loneliness, therefore, is not merely sadness. It is a biological environment. This does not mean that every form of distress stems from a lack of relationships, nor that simply “being with others” is enough to heal. That would be a naive oversimplification.
Rather, it means that human beings have evolved within this bond, and that the perception of being welcomed, protected, and not excluded can profoundly influence the way the body interprets the world.
The vagal pathway also extends into another crucial area: that of communication between the nervous system and the immune system. Kevin J. Tracey has described the so-called “inflammatory reflex,” a mechanism through which the nervous system helps regulate the inflammatory response. Subsequent studies, including some by Tracey himself, have explored the role of the vagus nerve in linking immunity, metabolism, and inflammation.
Here, too, it is important to avoid misinterpretations. It does not mean that “calming down” cures diseases. It does not mean that a sick person has been unable to regulate themselves. That would be an unfair and dangerous interpretation.
It means, more profoundly, thatthe body is an integrated system: stress, the sense of protection, relationships, immunity, sleep, breathing, digestion, and emotional memory are in constant communication with one another.
In this dialogue, breathing occupies a special place. Breathing slowly and regularly can influence certain parameters of autonomic regulation, including heart rate variability (HRV). A systematic review and meta-analysis published in 2022 by Sylvain Laborde, Mark S. Allen, Borges, and colleagues analyzed the effects of slow voluntary breathing on heart rate and HRV, finding effects on parameters related to parasympathetic regulation.
HRV-based biofeedback has also been the subject of study. A systematic review and meta-analysis published in 2020 by Paul Lehrer and colleagues evaluated the effectiveness of these interventions on various aspects of emotional and physical health and performance, with promising results—though these must always be interpreted in light of the quality of the studies and the context of application.
However, no single practice is a universal shortcut.
Breathing, walking, singing, meditating, sleeping better, reducing constant exposure to conflict, and spending time in emotionally safe environments—all of these can support the nervous system. However, they do not replace a diagnosis, therapy, or treatment when they are necessary.
Perhaps the greatest lesson of the vagal system is not that we must learn to calm ourselves on command. It is that we must recognize which environments, which people, which rhythms, and which words allow the body to avoid living constantly on the defensive.
Safety is not passivity. It is not naivety. It is not weakness. It is the biological condition that allows strength not to become armor. It is what allows a person to look at another without immediately perceiving them as a threat. It is what transforms a room into a livable space, a voice into an anchor, a relationship into a possible territory.
In Italy as in America—whether in a home, a clinical setting, a hotel, a healthcare facility, or an intimate relationship—safety is not an emotional detail. It is a fundamental condition. In a world that constantly demands performance, speed, and control, talking about the vagal system means refocusing our attention on something more ancient and more human: the need to feel safe in order to live fully.
Not just functioning. Not just enduring. Living.
Let’s return, then, to that woman who checked into the hotel that night. The city outside keeps moving. Cars stream by. Phones vibrate. The lights stay on. Nothing in the world has suddenly become simple.
But she received a tiny, decisive signal: a steady gaze, a calm voice, a non-intrusive gesture. She takes the key, goes up to her room, and sets down her suitcase. For the first time in many hours, she truly exhales.
The journey isn’t over. But her body has finally stopped preparing to flee. And in that silent, almost invisible breath, the grammar of safety begins anew.
