PTSD 3 No, It’s Not All In Your Head: The Vagus Nerve
- Kathy Morelli
- Oct 23, 2020
- 6 min read
Updated: Jan 29
Originally posted October 24, 2020.
This article explores the vagus nerve, polyvagal theory and trauma recovery in an educational, non-graphic way. You can read slowly or pause at any point.
Nerves Need Time to Heal, Just Like Any Other Physical Part of Us
A little background about the brain, nervous system, trauma and traumatic memories … (stuff that you probably already know but maybe forgot…)
Nerves are actually physical entities that can suffer damage.
Since the nerves are actually physical they can suffer actual damage from physical and emotional trauma.
And, the nerves are the communication system connecting the brain and body. This communication system is a two way, back and forth, signaling system, with the brain and body receiving and sending messages to and from each other.
When a person has PTSD, the communication signals via the nervous system, between brain and body, are changed. The nerves that connect to organs help us breathe, digest, sleep. If these nerves are over-stimulated and stuck in a trauma reaction, our breathing becomes shallow, our digestion is messed up, and our sleep is disrupted.
When we think about healing, we often imagine insight, understanding, or emotional processing. But trauma also affects the physical structures of the nervous system — and those structures need time.
The nerves need time to heal, like any other physical part of us.
Just as a muscle or bone does not heal instantly, nerves recover gradually. They adapt through repeated experiences of safety, rest, and regulation.
This is especially important to remember with trauma, where the nervous system may have spent long periods under threat.
Slow change is not a sign that something isn’t working. It is often a sign that healing is occurring at a biological pace.
The Cranial Nerves Are Direct Pathways Between Brain and Body
The human nervous system includes twelve cranial nerves that emerge directly from the brain and connect it to the body.
These nerves play essential roles in:
Sensation
Movement
Facial expression
Swallowing
Breathing
Heart rate
Vocal tone
Unlike spinal nerves, cranial nerves form direct communication pathways between the brain and organs involved in survival and social connection. Because of this, they are deeply involved in how we experience stress, safety, and regulation.
The Vagus Nerve: The Tenth Cranial Nerve
The Vagus Nerve, the tenth cranial nerve, is the longest of the cranial nerves. It travels from the brainstem down through the neck into the chest and abdomen, connecting the brain to the heart, lungs, and digestive system.
The Vagus Nerve is involved in mood, stress levels, pain levels, inflammatory responses, breathing, vocalization, and organ responses such as heart rate, gastric juice production, digestion, breathing rate, etc .
The Vagus Nerve plays a central role in:
Regulating heart rate
Supporting digestion
Influencing breathing patterns
Modulating inflammation
Supporting states of calm and connection
Because of its wide reach, the Vagus Nerve is especially sensitive to experiences of threat and safety.
Polyvagal Theory and the Autonomic Nervous System
Stephen Porges’ Polyvagal Theory builds on more than a century of research on the autonomic nervous system (ANS).
Traditionally, the ANS was understood as having two primary branches:
The sympathetic nervous system, associated with fight or flight
The parasympathetic nervous system, associated with rest and restoration
While this framework is still useful, it does not fully explain the range of responses people experience under extreme or prolonged threat.
Dr. Porges expanded this understanding by closely examining the Vagus Nerve, a major pathway connecting the brain and body. His work highlighted that the vagus nerve is not a single, uniform system, but includes distinct pathways with different functions and evolutionary origins.
Three Adaptive Pathways of the Autonomic Nervous System
From a polyvagal perspective, the nervous system responds to threat in a hierarchical and adaptive way, prioritizing survival over conscious choice.
Social engagement (ventral vagal): safety through connection
When we sense danger, the body’s first biological strategy is often to seek safety through engagement. This response is supported by the ventral vagal pathway, which allows us to use social connection—eye contact, voice, facial expression, and negotiation—to reduce threat. We may try to talk, reason, or de-escalate a situation. This is not a cognitive decision; it is a nervous system response oriented toward survival through connection.
Mobilization (sympathetic): safety through action (fight or flight)
If engagement does not restore safety, the nervous system shifts toward mobilization, activating the sympathetic nervous system. This is the familiar fight-or-flight response, characterized by increased heart rate, muscle tension, and readiness for action.
Immobilization or freeze (dorsal vagal): safety through shutdown
When neither engagement nor mobilization is possible—when there is no effective way to fight or escape—the nervous system may move into a final protective state often described as freeze or tonic immobility. In polyvagal terms, this involves dorsal vagal shutdown.
These pathways are not choices or personality traits.
They are automatic survival responses shaped by perception of safety or threat.
Freeze and Dorsal Vagal Shutdown
During dorsal vagal shutdown, the body reduces engagement with the external world. People may experience numbness, dissociation, altered awareness, reduced movement, or a sense of disconnection. These responses are biological and automatic—they are not choices, and they are not signs of weakness.
In this state, the nervous system is flooded with neurochemicals that help protect against overwhelming pain and threat. These changes can:
Dampen emotional and physical pain
Interfere with rational thought
Reduce muscle tone or movement
Affect how memories are encoded
Because of this, experiences that occur during extreme threat may be remembered in fragmented, sensory, or non-verbal ways rather than as a clear narrative.
Research suggests that a significant number of people exposed to overwhelming threat—particularly in situations where escape is impossible—experience some form of tonic immobility. Understanding this response is essential for reducing shame and self-blame.
What Does This Have to Do With PTSD?
A great deal.
PTSD symptoms can be understood as the nervous system becoming biased toward certain survival pathways, often long after the original danger has passed.
When the body repeatedly detects threat, it may rely more heavily on mobilization or shutdown responses, even in relatively safe situations.
Understanding PTSD through this lens helps explain why trauma responses are so persistent and why healing involves working with the nervous system rather than trying to reason symptoms away.
Body-Based Memory and Trauma Symptoms
The nervous system retains the physiological patterns associated with these protective states. Long after the original event has passed, cues that resemble the original threat can activate similar bodily responses.
When trauma is recalled or discussed, the body may re-enter aspects of the original state, such as:
Dissociation or numbing
Blankness or difficulty finding words
Changes in breathing or sweating
Reduced emotional access
A sense of “shutting down”
These responses are not signs that someone is failing to heal. They reflect the nervous system re-engaging protective strategies that once helped the person survive.
Because these responses are non-verbal and physiological, they cannot be resolved through insight or conversation alone.
Why Somatic Approaches Matter
Somatic and body-based therapies work directly with these non-verbal responses. Rather than asking the nervous system to override protective states, they focus on:
Increasing awareness of bodily sensation
Supporting regulation without forcing exposure
Allowing new experiences of safety to emerge gradually
At the same time, many people benefit from developing a meaningful narrative—one that acknowledges the body’s responses as adaptive rather than defective. Over time, integrating bodily regulation with narrative understanding can support a more coherent sense of self and experience.
Practices that support nervous system regulation may help translate understanding into lived experience.
Mindfulness practices that support regulation
Distress tolerance skills for nervous system activation
This article is part of the series No, It’s Not All in Your Head, which explores trauma through the lens of the nervous system.
Bibliography
Clancy, Deuchars, & Deuchars, 2013. The wonders of the wanderer. Experimental Physiology, Jan, 98(1) p. 38-45. https://rdcu.be/bZf00
Dana, D. (2018). The polyvagal theory in therapy. New York: W.W. Norton & Conpany.
Kain, K. and Terrell (2018). Nurturing resilience. Berkeley, California: North Atlantic Books
Hannaford, C. (1995), Smart Moves: Why learning is not all in your head. Salt Lake City, Utah: Great River Books
Rosenberg, S. (2017). Accessing the healing power of the vagus nerve. Berkeley, California: North Atlantic Books
Van Der Kolk, B. (2014). The body keeps the score. Penguin Books: New York.
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