How Trauma Affects the Nervous System and How You Can Heal It?
When we experience trauma, our body remembers what our mind tries to forget. To survive, the nervous system learns to use patterns and detect threats as soon as possible. But those same efforts to survive perpetuate a system that makes us forget how to feel safe and calm. Scanning for threats, we stay mobilized and vigilant, unable to relax.
When we work to heal from trauma and its effects, the mind plays a significant role. Thoughts, images, and endless ruminations all come from the mind’s effort to work around flashbacks and triggers. But another segment, the nervous system, is often overlooked. Recovering from trauma is nearly impossible if our nervous system, which controls our automatic reactions, isn't healed.
This post will delve into the structure of the autonomic nervous system and the proposed polyvagal theory, which has changed the way we define neurological states. From there, we will explore how these neurological theories support EMDR and somatic therapies in their efforts to heal trauma. Let’s start from the beginning.
Understanding the Autonomic Nervous System
The autonomic nervous system (often abbreviated as ANS) is the body’s automatic regulator. It controls the automatic processes that we don’t consciously direct, i.e., heartbeat, breathing, digestion, and emotional arousal. ANS works behind the scenes, constantly scanning for cues of safety or threat and adjusting our physiology to match what it perceives in the outside world.
The ANS has two primary branches:
Sympathetic Nervous System (also called the Fight or Flight)
This branch is the so-called fight or flight system, which is a characteristic reaction to threatening situations. When activated, it mobilizes energy and prepares the body to respond to danger. Heart rate increases, muscles tense, and attention narrows so that the organism can focus on surviving immediate threats.Parasympathetic Nervous System (so-called Rest and Digest)
This system restores balance after the danger passes. It is characterized by a slower heart rate, deeper and slower breathing, as well as overall relaxation, which enables digestion, social engagement, and recovery. It’s the body’s natural brake that allows us to feel safe, connected, and calm.
In a healthy system, these two branches work in rhythm. We mobilize when we need to, then return to rest when the threat is gone. Trauma, however, disrupts this natural flow. When experiences of danger are overwhelming or chronic, the nervous system can get stuck in survival mode. So, in a way, the body forgets to “shift gears” and instead of relaxing once the threat is gone, it stays dysregulated as it was during the traumatic experience. This dysregulation can go two ways:
Some linger in a on‑alert mode (clinically termed hyperarousal), feeling constantly anxious, jumpy, or simply unable to let go, even when the surroundings are completely safe.
Others go through a shutdown or numbness (hypoarousal), a sort of state in which their energy, emotions, and sense of engagement seem to vanish.
To learn more about the survival states of hyper- and hypo-arousal, visit our post on that (and another, correlated topic).
The nervous system has learned that the world is unsafe, so it continues to react as though the threat is present. Whenever a trigger pops up, it can feel like the same painful memories are unfolding once more, and the nervous system reacts the best way it can to prevent re-traumatization. Recognizing this process can help you shift the narrative - nervous system reactivity is not a malfunction, but a protective mechanism that does its best to stay alive.
How Trauma Leaves Its Imprint on Autonomic Regulation
When a traumatic experience happens, the nervous system looks for ways to protect itself and prevent further pain. The amygdala, the brain's “threat detector,” fires up and becomes overreactive, often signaling danger. The body gets these signals, remains in constant readiness (fight-or-flight mode), and stress hormones circulate over and over again. The nervous system, looking to prevent and protect, learns to perceive even neutral cues (tone of voice, a facial expression, a sudden sound) as potential threats. This hormonal imbalance impairs the organism’s ability to return to a calm parasympathetic state, and the body stays alerted for prolonged periods of time.
This process is particularly important in cases of early developmental trauma (like neglect, inconsistency, or prolonged fear) or in chronic traumatic experiences. These experiences (when they happen early on or repeatedly) shape the stress response system, practically developing it to be overalert. In these cases, the nervous system learns instability as its baseline. The capacity for regulation, co-regulation, and safety never fully develops, making adult stress responses more reactive and harder to soothe. The process is two-fold: on one side, the nervous system was (over time) built to be highly active and sensitive to threats, and on the other side, that sensitivity causes intense reactions to even slight triggers, reinforcing the existing dysregulated pathways.
Research conducted by Schauer and Elbert supports these observations: trauma can shift baseline arousal and weaken vagal tone, the marker of our ability to self-regulate and feel safe in the body. The same mechanisms that once ensured survival now keep the organism stuck in arousal.
Individuals with nervous system dysregulation can experience a range of symptoms. Some experience anxiety and panic attacks, emotional flooding, or physical symptoms like a racing heart or gastrointestinal problems. Others are prone to shutdown and numbness, often feeling detached from themselves and their surroundings, and emotionally flat. This brings us to the polyvagal theory, the theory that explains that the ANS doesn’t work in black and white.
Polyvagal Theory for Understanding Safety and Connection
As explained in the previous section, traditional psychology teaches that the nervous system has two main modes: “fight or flight” and “rest and digest.” Dr. Stephen Porges’ Polyvagal Theory expanded this understanding, offering an upgraded view of how our bodies respond to safety and threat. This theory focuses on the vagus nerve, the longest cranial nerve that connects the brain to the heart, lungs, and gut. In his polyvagal theory, Dr. Porges explains how the vagus nerves’ different branches shape our emotional and physiological states.
According to Polyvagal Theory, the autonomic nervous system doesn’t have only 2 states; it has 3. It doesn’t only track “danger on” and “danger off”, but also has a “danger overwhelm” state. A good analogy would be to imagine your body as a traffic light with three lights.
Ventral Vagal (Safety and Connection)
This is the “green light” state, where we feel calm, curious, and socially engaged. The body is regulated, breathing is steady, and we can think clearly, connect with others, and experience joy.Sympathetic (Alertness and Mobilization)
Represented by the “yellow light,” this state prepares the body for action. Heart rate increases, muscles tense, and the focus shifts to survival - fight or flight. Short-term, this state is adaptive; but prolonged, it becomes exhausting.Dorsal Vagal (Shutdown)
The “red light” state is one of collapse and conservation. When escape feels impossible, the body shuts down: energy drops, emotions go numb, and dissociation may occur. It’s a biological form of self-protection through dissociation, when we distance ourselves from what is going on to protect ourselves from what feels like “way too much”.
Traumatic experiences sensitize the whole system, and the nervous system may start staying in yellow and red states, misinterpreting safety as danger. A system that is supposed to move between safety and alertness starts moving between alertness and shutdown. Everyday stressors can feel life-threatening, and even moments of calm may feel unsafe, with danger lurking around.
The goal of trauma therapy is to help clients recognize in which state they are and slowly learn skills to move safely back toward their inner “green” light. By increasing awareness, noticing safety and danger cues, and learning body-based regulation, clients who work with EMDR or somatic approaches can retrain their nervous system to trust connection again.
How Polyvagal Theory Enhances EMDR and Somatic Therapies
Since the first publication of the Polyvagal theory in 1995, it has become an essential framework that helps mental health experts better understand the impact of trauma and provide a more effective support for nervous system regulation. Today, many modalities use polyvagal theory, and its frameworks are especially important for trauma therapies like EMDR and Somatic experiencing. Today, it is widely recognized that healing happens through states of so-called felt safety (clients’ perceived and bodily experienced safety). Therapists now use this model to fine-tune the pacing of therapy, help clients deepen embodiment, and enhance integration across multiple trauma modalities.
EMDR (Eye Movement Desensitization and Reprocessing)
EMDR uses bilateral stimulation like eye movement, tapping, or sounds to help the brain reprocess traumatic experiences. While the brain is engaged in the stimulation, the client is advised to think about certain parts of the traumatic experience, be it particular emotions, pictures, sounds, or sensations. This dual attention helps the brain integrate previously fragmented experiences, reducing the emotional intensity of triggers and calming overactive survival responses. In essence, EMDR helps clients to overcome the traumatic memories that keep their nervous system stuck in danger mode.
From a Polyvagal perspective, EMDR works best when sessions occur within a client’s window of tolerance, i.e., the zone where they can process without becoming overwhelmed or shut down. I’ve written on this topic extensively, so feel free to head over to the blog about the window of tolerance. In essence, when combining EMDR and polyvagal principles, therapists can observe and notice subtle physiological cues like facial expressions, muscle tensions, and breath rates to ensure that the client’s nervous system is within the optimal range to be able to reprocess memories most effectively. If the client gets into activation, they switch to grounding or resourcing interventions to reestablish safety before moving forward.
Polyvagal theory is an invaluable framework that helps EMDR therapists follow and support their clients effectively and safely. EMDR, done in such a way, not only helps the mind to change the way it remembers the trauma, but it also helps the body relearn safety in the present moment.
Somatic & Body-Based Therapies
Approaches such as Somatic Experiencing and Sensorimotor Psychotherapy work directly with the body’s physical responses to trauma. Opposed to EMDR, these therapeutic modalities don’t focus on revisiting the memories and redefining their meaning. Instead, they focus on completing unfinished (stuck) responses and impulses that the body didn’t fulfill or were interrupted during the original event. Somatic experiencing uses physical cues and movement to release and finish stuck survival responses like fight, flight, or freeze.
With somatic experiencing, clients pay attention to their interoceptive and proprioceptive (inner) sensations and movements that give them signs of the state of their nervous system. Once aware, clients are then prompted to track and soothe these sensations, bringing their nervous system through the whole cycle from arousal to safety.
Polyvagal theory enriches somatic experiencing by proposing small doses of distress (as practiced by exposure therapies), which the client can integrate without getting into one of the overwhelmed states. This process, with time, builds the nervous system’s capacity for self-regulation and trigger tolerance. On top of that, this activation helps the body regain trust in its ability to mobilize and then return to calm, essentially increasing the client’s self-esteem to regulate themselves.
Integration of EMDR and Somatic therapies
When EMDR’s cognitive and emotional reprocessing is combined with somatic (bodily) awareness, the healing process deepens and becomes holistic. Polyvagal-informed therapists consider and note physiological markers (breath rhythm, vocal tone, posture) to pace sessions according to the body’s readiness.
The goal of these joint modalities and interventions is not to erase trauma but to restore flexibility and connection by helping the nervous system move fluidly between states of activation and rest. Trauma therapy teaches the body and brain that safety, connection, and vitality are once again possible and guides the client to learn their way to it.
A Few Ending Words
Trauma recovery is ultimately the process of teaching the nervous system to feel safe again. Healing from trauma becomes possible when the body learn that it doesn’t need to continuously stay alert and in defense mode. The aim is not to erase the past but to restore flexibility and enable the nervous system to move between activation and calm, without staying stuck in either. Polyvagal-informed EMDR and body-based therapies are powerful modalities that guide clients toward this goal.
If you feel caught in cycles of anxiety, shutdown, or disconnection, EMDR or trauma-focused somatic therapy can help you learn how to regulate your nervous system. With the right guidance by our EMDR and polyvagal theory-informed therapists, your nervous system can safely learn to move from survival into connection, and from fear to grounded aliveness. Contact us today and schedule your session to take the next step toward freedom, resilience, and authentic connection.
Resources
Schauer, M., & Elbert, T. (2010). Dissociation following traumatic stress: Etiology and treatment. American Psychological Association. https://psycnet.apa.org/record/2010-19607-007
Porges, S. W. (2011, November). The polyvagal theory: Neurophysiological foundations of emotions, attachment, communication, self-regulation. Journal of the Canadian Academy of Child and Adolescent Psychiatry. https://pmc.ncbi.nlm.nih.gov/articles/PMC3490536/