How Trauma Impacts the Nervous System
A introductionary plain-English guide backed by science
Have you ever felt your heart pound before something big, or your hands tremble before a hard conversation? That's your nervous system working exactly as designed; it’s gearing you up to meet a challenge. But imagine that same alarm system develops a hair-trigger sensor: it doesn't wait for smoke. A sneeze sets it off. And once it's blaring, it won't stand down until every inch of the space has been searched, cleared, and cleaned.
That's what nervous system dysregulation can look like after trauma. The alarm isn't malfunctioning out of weakness or oversensitivity; it learned to fire that way because, at some point, the danger was real, and this smart little fictional device learned to watch out for the threat again.
We know you can't simply tell a biological system to behave, any more than you can shout at a smoke detector and expect it to function as new or desired.
It takes reprogramming.
It takes replacing worn parts and know how.
The house itself isn't the problem; it's the device that has adapted in the only way it knows how, and it’s not working for the residents. So the device needs some work.
So it is for us. We can think of ourselves as less than because we have trauma, but we need to address it.
Trauma isn't just something that happens in your mind. It takes up residence in your body. Like a wormhole punched through time, it can transport the sensations of a past moment directly into the present with a racing heart, a tightened chest, a wave of dread, or even when you have no conscious memory of the original experience. Your nervous system remembers what your thoughts have long since let go of.
That's why understanding the science of trauma isn't just academic. It's one of the most compassionate things you can do for yourself. Trauma and fear are close companions, and both thrive in the unknown. Learning how they operate and practicing the skill of noticing and naming them when they arise are among the most grounding steps you can take toward no longer being ruled by their pull.
Lets Learn
Your Brain's Alarm System: Fight, Flight, and Freeze
To understand a little more about how trauma impacts the nervous system, we need to understand the nervous system’s basic and relevant functions related to trauma.
Think of your brain as a really sophisticated security system. Deep inside, in a region called the amygdala (pronounced ah-MIG-duh-lah), there's a tiny structure that acts like a smoke detector. The moment it senses danger like a loud noise, a threatening face, even a smell linked to a bad memory — it fires an alarm.
That alarm triggers one of three ancient survival responses:
Fight: Your body floods with adrenaline. Muscles tense. You feel ready to confront whatever is threatening you.
Flight: Energy surges into your legs. Your heart rate spikes. Your whole system screams, "Get out of here!"
Freeze/Shutdown: When fighting or running feels impossible, the nervous system hits the brakes hard. You go still, numb, or dissociated like a deer in headlights.
These aren't choices, they're automatic, survival-level responses that fire before your thinking brain ever gets a chance to weigh in. Think of it like a futuristic force field: it detects and responds to a threat before the threat even appears on your radar. The prefrontal cortex, the part of your brain responsible for reasoning, logic, and decision-making, essentially goes offline the moment the alarm sounds. Which is why you can't argue someone out of a panic response, and why telling a person to "just calm down" when their amygdala is activated is akin to shouting instructions at a force field. The system isn't listening to words right now. It's in full protection mode.
In a truly dangerous situation, these responses are lifesaving. The problem is that after trauma, the amygdala can get hypersensitive, like a smoke detector that now goes off every time you make toast. This is the beginning of nervous system dysregulation.
Here's the hopeful part: none of this is permanent, even for those with adrenal fatigue. The nervous system can learn, adapt, and reset —and we'll touch on how a little further on.
Research Note: Neuroscientist Joseph LeDoux's foundational work on the amygdala showed that fear responses travel a "low road" (a fast, direct neural pathway) that completely bypasses conscious thought. This is why trauma reactions can feel so out of control because they literally are. (LeDoux, J.E. The Emotional Brain, 1996; Neuron review 2015)
Polyvagal Theory: The Three Gears of Your Nervous System
Understanding Polyvagal Theory will help conceptualize what is happening in your body when it is responding to its environment even deeper.
In the 1990s, a neuroscientist named Dr. Stephen Porges developed something called Polyvagal Theory, and it changed the way therapists and researchers think about trauma.
Some of you who already know the theory may know this already, but it's worth noting that as of 2026, Polyvagal Theory has faced some academic pushback, with a growing number of researchers questioning aspects of its neurological and anatomical claims. The debate is ongoing, and the critiques are worth being aware of. That said, the current consensus among clinicians, and my own reading of the available evidence, is that the theory remains a genuinely useful framework in practice. The criticism is real, but it isn't yet substantial enough or consistent enough to retire the model. Think of it less as settled science and more as a working map, imperfect, but still one of the better ones we have.
The theory centers on the vagus nerve — the longest nerve in your body, running from your brainstem all the way down to your gut and it plays a massive role in how safe or threatened you feel at any given moment.
Polyvagal Theory proposes that your autonomic nervous system (the part you don't consciously control) operates in three distinct states:
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When you feel genuinely safe, your nervous system is in its highest, most evolved gear. Your voice has warmth, your face is expressive, you can make eye contact, and you're able to connect with other people. Digestion works well. Sleep is possible. You can think clearly.
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When the brain (including the amygdala, as mentioned above) detects a threat, the sympathetic nervous system kicks in. Heart rate rises. Breathing becomes shallow and fast. Digestion shuts down (your body doesn't care about digesting your lunch when you might be a predator’s lunch). You're mobilized for action.
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When the threat feels completely overwhelming and there's no escape, the nervous system drops into its oldest, most primitive gear: shutdown. Heart rate slows. The person may feel numb, collapsed, dissociated, or "checked out." This is the freeze response, and in the animal world, it's the equivalent of playing dead.
And that disruption doesn't stay in one place. After trauma, people can get stuck cycling between the sympathetic (fight/flight) and dorsal vagal (shutdown) states, never quite able to find their way back to the ventral vagal, the safe, social state where connection and healing actually become possible. Understanding this cycle isn't just fascinating neuroscience. It's the foundation of modern trauma therapy, and it's why so many effective treatment approaches work with the body, not just the mind. We'll be exploring the practical applications of these theories in upcoming posts, so if this resonates with you, stay tuned.
Research Note: Dr. Porges' original paper on Polyvagal Theory was published in the journal Psychophysiology in 1995. His 2011 book The Polyvagal Theory expanded the clinical applications significantly. Dozens of peer-reviewed studies have since used polyvagal principles to inform trauma therapy protocols, including EMDR and somatic therapies. (Porges, S.W. Psychophysiology, 1995; 32(4):301–318)
Enteric Nervous System (ENS): Your Second Brain
One often overlooked player in the trauma-nervous system conversation is the Enteric Nervous System (ENS), the vast network of neurons embedded in the lining of your gastrointestinal tract. With an estimated 500 million nerve cells, the ENS operates with remarkable independence from the brain, regulating digestion, immune response, and gut permeability largely on its own. But independent doesn't mean disconnected. Through the vagus nerve, the ENS and the central nervous system are in constant two-way dialogue. What’s interesting is that trauma disrupts that conversation profoundly. Chronic nervous system dysregulation has been directly linked to IBS, gut inflammation, and altered gut microbiome composition. So when your stomach churns during a stressful moment, it isn't being dramatic. It's participating in the same threat response your brain is running, just from a different floor of the building.
Research Note: Mayer, E.A. et al. (2015) published a landmark review in Nature Reviews Neuroscience mapping the gut-brain axis and its role in stress and emotional regulation. Their findings underscored the ENS not as a passive bystander but as an active participant in how the body processes and stores stress. (Mayer, E.A., Tillisch, K., & Gupta, A. — Nature Reviews Neuroscience, 2015; 16(8):461–474)
When Trauma Lives in the Body: Somatic Symptoms
"Somatic" just means "related to the body." And one of the most important things trauma research has taught us over the last 30 years is that trauma doesn't only shape your thoughts and emotions, it physically changes your body.
Dr. Bessel van der Kolk, a leading trauma researcher and psychiatrist, wrote a book called The Body Keeps the Score (2014) that became a cultural phenomenon for one simple reason: millions of people recognized themselves in it. His argument, backed by decades of research, is that trauma gets encoded in the nervous system and resurfaces as physical symptoms, often long after the original experience has passed.
Common somatic symptoms of trauma and nervous system dysregulation include:
Chronic muscle tension and pain: Muscles that never fully relax — jaw clenching, neck and shoulder tightness, lower back ache. The body quietly bracing for a threat that isn't there.
Breathing irregularities: Shallow breathing, breath-holding, or hyperventilation. The nervous system keeping the body on a low hum of readiness.
Digestive issues: IBS, nausea, appetite disruption, and stomach pain — all connected back to the enteric nervous system and its direct line to the vagus nerve.
Skin reactions: Eczema flares, hives, and rashes driven by stress hormone activity and immune dysregulation.
Fatigue: Not ordinary tiredness — the kind of depletion that comes from a body that has been running a threat response in the background for months or years.
Dissociation: Feeling detached from your own body, watching yourself from the outside, or the world around you not feeling quite real.
Sleep disturbances: Difficulty falling or staying asleep, hypervigilance at night, or vivid trauma-related nightmares.
Headaches and migraines: Frequently reported in trauma survivors and linked to chronic nervous system activation and muscle tension patterns.
In more extreme cases,somatic symptoms can include:
Functional Neurological Disorder (FND), formerly known as Conversion Disorder
Psychogenic Nonepileptic Seizures (PNES)
Unexplained chronic pain
and Akinetic (Stuporous) Catatonia
To name a few. These aren't random. They're the body doing whatever it takes to signal that something unprocessed still needs attention. So if this sounds familiar to your life, consider giving your body the attention and care it is asking for.
Here's the part worth sitting with: addressing these symptoms doesn't always require years of expensive treatment. Something as accessible as intentional deep breathing, practiced consistently, has measurable effects on nervous system regulation. It won't fix everything, and it isn't a substitute for deeper work. But it can meaningfully increase a sense of calm and life satisfaction, making things easier to handle, even when life itself hasn't changed. That being said, if you are struggling, please seek assistance.
Research Note: A landmark meta-analysis published in JAMA Internal Medicine (Hughes et al., 2017) found strong associations between adverse childhood experiences (ACEs) and somatic health outcomes including headaches, back pain, and gastrointestinal disorders — one of many studies supporting the idea that the body physically registers and holds psychological distress.
The Chronic Illness Connection
Here's something that surprises a lot of people: trauma and unresolved nervous system dysregulation are genuinely linked to chronic physical illness. This isn't saying "it's all in your head" — quite the opposite. It means that psychological stress causes measurable, biological changes in the body over time.
The HPA Axis and Cortisol Dysregulation
One example of this is at the hormonal level, trauma activates what's known as the HPA axis, the hypothalamic-pituitary-adrenal axis, the body's central stress-response system. When it's working as intended, this system releases cortisol to help you rise to a challenge, then dials back down once the threat has passed. But chronic trauma disrupts that rhythm. Cortisol output can run too high for too long, burning through the system and, in some cases, eventually swinging too low, leaving the body in a kind of hormonal flatline.
Many people recognize this pattern through the term adrenal fatigue, and while it's a useful shorthand for a very real set of symptoms, it's worth knowing that the clinical picture is more complicated.
The term hasn't been formally recognized by any Endocrinology society, and a 2016 systematic review of 58 studies found no consistent scientific evidence to support that adrenal glans were impaired as a defined clinical condition. (Cadegiani & Kater, 2016) The more accurate framing is HPA axis dysregulation — less catchy, but better supported by the research.
Either way, the experience points to the exhaustion, the brain fog, the psychosomatic symptoms, and the sense of running on empty are real, and it has real roots in what chronic stress does to the body over time.
When our body responds and holds onto trauma, we can become chronically ill and carry all the additional struggles that that entails. This can include anything from aging faster to disrupting our immune system.
The Immune System Connection
Chronic stress and trauma-related nervous system dysregulation have been shown to produce systemic inflammation, a low-grade, ongoing activation of the immune system. Inflammation is now understood to be a contributing factor in conditions like:
Autoimmune disorders (like lupus, rheumatoid arthritis, and Hashimoto's thyroiditis)
Cardiovascular disease — chronic activation of fight-or-flight raises blood pressure and damages arterial walls over time
Type 2 diabetes — cortisol dysregulation affects blood sugar regulation
Fibromyalgia — characterized by widespread pain and fatigue, with strong nervous system dysregulation connections
Chronic fatigue syndrome (ME/CFS) — emerging research points to HPA and immune system dysregulation
The key mechanism linking trauma to chronic illness is prolonged allostatic load — a term that describes the cumulative "wear and tear" on the body from ongoing stress responses. When the nervous system can't return to a regulated, safe baseline, every system in the body suffers over time.
Importantly, this research doesn't mean illness is "your fault" or that stress caused your condition. It means that addressing nervous system dysregulation through trauma therapy isn't just good for mental health — it may be genuinely protective for physical health, too.
Research Note: The ACE (Adverse Childhood Experiences) Study — one of the largest investigations of childhood trauma and health outcomes, conducted by the CDC and Kaiser Permanente — found a dose-response relationship between ACE scores and risk for heart disease, cancer, diabetes, and autoimmune disorders. People with 4+ ACEs had dramatically higher rates of chronic illness. (Felitti, V.J. et al. — American Journal of Preventive Medicine, 1998; 14(4):245–258)
“Patients may not have caused all their own problems, but they have to solve them anyway.”
What Does Healing Look Like?
Here is the part where we get to exhale a little because there is genuinely good news.
The nervous system is neuroplastic. That word means it is capable of change, adaptation, and — with the right conditions — healing. You may have heard the saying "you can't teach an old dog new tricks." Neuroscience has largely proven that wrong. The brain retains the ability to form new neural connections, rewire automatic responses, and learn new ways of feeling safe throughout a person's entire life. Your thoughts, feelings, and nervous system patterns are not fixed. They were shaped by experience — and experience can reshape them.
That said, this isn't a process you just decide your way through. Healing from trauma takes time, consistent effort, and in many cases professional support — which is exactly what trauma-informed therapists are trained to provide. It's one reason people return to therapy again and again, or stay in it for years. That's not failure. That's the reality of doing deep, brave, and intentional work. It means choosing — sometimes over and over — to evolve rather than just survive.
Below are some of the most widely used and researched approaches to trauma therapy and nervous system regulation. This list is not exhaustive, and different approaches work better for different people. A good therapist can help you figure out what fits.
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One of the most extensively researched trauma treatments in the world. Trauma-focused CBT (TF-CBT) works by identifying and gently challenging the thought patterns and beliefs that trauma installs — things like "I am not safe" or "I deserved it." The VA/DoD Clinical Practice Guidelines list TF-CBT among the highest-recommended trauma treatments, alongside EMDR and Prolonged Exposure. (Bisson et al. — Cochrane Database of Systematic Reviews, 2013)
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Originally developed by Dr. Marsha Linehan for people with severe emotional dysregulation, DBT has become a cornerstone tool for trauma survivors — particularly those with complex or early-childhood trauma. It combines mindfulness, distress tolerance, emotional regulation skills, and interpersonal effectiveness training. Research consistently shows it reduces self-harm, emotional dysregulation, and PTSD symptoms in complex trauma populations. (Linehan et al. — Archives of General Psychiatry, 2006)
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Developed by Dr. Richard Schwartz, IFS maps the inner world as a system of "parts" — subpersonalities that formed, often in childhood, to help us survive difficult experiences. Rather than trying to eliminate these parts, IFS works to understand and integrate them through a compassionate internal relationship with the Self. A 2021 pilot study published in the Journal of Aggression, Maltreatment & Trauma found that IFS therapy had significantly positive effects on adults with PTSD and histories of exposure to multiple forms of childhood trauma. A more recent 2024 study published in Psychological Trauma (APA) found that an online group-based IFS program led to clinically meaningful PTSD symptom reduction in 53% of participants, along with decreases in anxiety, depression, and suicide risk. The research base is still growing, but the early signals are strong.
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Developed by Dr. Peter Levine, SE works directly with the body's incomplete survival responses — the freeze, fight, or flight energy that got activated during trauma and never fully discharged. Rather than asking clients to retell or reprocess the narrative of what happened, SE uses gentle, body-oriented techniques to help the nervous system complete those interrupted responses and return to regulation. A 2021 scoping literature review found preliminary evidence that SE produces positive effects on PTSD-related symptoms, as well as improvements in depression, pain, and overall well-being in both traumatized and non-traumatized samples. The research base is still developing, and larger randomized controlled trials are ongoing — but the clinical results have been consistently promising for over four decades of practice. (Kuhfuß et al. — European Journal of Psychotraumatology, 2021; Payne, Levine & Crane-Godreau — Frontiers in Psychology, 2015)
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One of the most studied trauma therapies in existence, EMDR uses bilateral stimulation — usually guided eye movements — to help the brain reprocess traumatic memories so they are stored as past events rather than ongoing threats. A systematic narrative review including multiple meta-analyses and randomized controlled trials found that EMDR improved PTSD diagnosis, reduced PTSD symptoms, and reduced other trauma-related symptoms — and was evidenced as being more effective than several other trauma treatments. For those weighing therapy against medication: a study comparing EMDR to fluoxetine (an antidepressant commonly prescribed for PTSD) found that EMDR was associated with greater symptom reduction than medication. Research also indicates that trauma-focused therapies like EMDR often work faster than medication approaches for PTSD. EMDR has official approval from the World Health Organization, the U.S. Department of Veterans Affairs, and government health organizations in the UK, Australia, and Germany, among others. (Seidler & Wagner — Psychological Medicine, 2006; VA/DoD Clinical Practice Guidelines; WHO Guidelines, 2013)
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Therapists trained in Polyvagal principles help clients learn to identify which nervous system state they're in — and use targeted tools like breathwork, movement, vocal toning, or safe social engagement to actively shift toward regulation. The work of Dr. Stephen Porges and clinicians like Deb Dana have translated polyvagal science directly into practical, session-by-session therapeutic skills.
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Slow, controlled breathing — particularly diaphragmatic breathing — directly stimulates the vagus nerve and measurably shifts the nervous system out of sympathetic activation. Even a few minutes of intentional breath practice has been shown to increase heart rate variability (HRV), a key marker of nervous system regulation and resilience. This is one of the most accessible, zero-cost tools available — and one of the most underestimated. (Zaccaro et al. — Frontiers in Human Neuroscience, 2018)
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According to both Polyvagal Theory and Gottman relationship research, one of the most powerful nervous system regulators we have is the experience of feeling genuinely safe with another person. Co-regulation — the process of one nervous system helping to calm and stabilize another — is not just a therapeutic concept. It's a biological need. Therapy, supportive friendships, group healing spaces, and community all contribute meaningfully to recovery. You were not meant to heal alone.
The Takeaway
If you've experienced trauma — abuse, neglect, loss, disaster, a hard childhood, or simply the slow accumulation of too much over too long — your body is not broken. It adapted. Your nervous system learned to stay alert to keep you safe, and at the time, that was exactly the right response. It may have even saved your life, and now it could be time to help it see that it can adapt again, this time hopefully to something that involves a little more peace, calm, and security in your life.
Understanding the mind-body connection isn't just interesting science. It's a guide map. One that explains why you react the way you do, why your body carries what it carries, and why certain people or moments can send your system into overdrive without warning. Most importantly, it points toward something worth holding onto: healing is real, and it is available to you.
Healing from trauma isn't about getting over it or pretending it didn't happen. Think of it like taking in a stray cat that has spent too many nights out in the cold — scared, guarded, and not quite sure the world is safe yet. You don't put it down. You don't lock it away and ignore it. You move slowly, offer patience, learn what startles it and what soothes it, and make sure it gets the care it needs. Little by little, at its own pace, it starts to trust that home is safe again. Meanwhile, life keeps going — you still have to show up, keep your commitments, and function in the world. You tend to the cat, without letting it run the house. That's the work. The goal is to help your nervous system slowly, safely learn that it is allowed to come back to balance.
We are learning more every year — and in an age of rapid technological change, the need to keep pace with our emotional intelligence has never been more important. The most powerful version of you isn't the one who avoids their inner world. It's the one who learns to move through it. You reading this right now is part of that important work to understand yourself and others.
This learning is so important because we know that trauma doesn't just sit quietly in the background. For many people, it determines what careers feel reachable, what relationships feel safe, what risks feel worth taking, and whether dreams feel allowed at all. It moves through families across generations — through nervous systems, patterns, and decades of unspoken things. You may be carrying so much more than you could ever imagine.
That's not your fault. But it is within your power to address. Educate yourself. Stay willing. Find a provider who knows this terrain and move at a pace that feels like a balance of comfort and just a little stretch. Your nervous system has been working overtime to protect you — it deserves the chance to finally rest.
“The world needs you healed, and so do you.”
References & Further Reading
• LeDoux, J.E. (1996). The Emotional Brain. Simon & Schuster. | LeDoux, J.E. (2015). Feelings: What Are They & How Does the Brain Make Them? Daedalus, 144(1).
• Porges, S.W. (1995). Orienting in a defensive world. Psychophysiology, 32(4), 301–318.
• Porges, S.W. (2011). The Polyvagal Theory. W.W. Norton & Company.
• Van der Kolk, B. (2014). The Body Keeps the Score. Viking.
• Felitti, V.J. et al. (1998). Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. American Journal of Preventive Medicine, 14(4), 245–258.
• Hughes, K. et al. (2017). The effect of multiple adverse childhood experiences on health. The Lancet Public Health, 2(8), e356–e366.
• Levine, P.A. (1997). Waking the Tiger: Healing Trauma. North Atlantic Books.
• WHO (2013). Guidelines for the Management of Conditions Specifically Related to Stress. World Health Organization.
• Cadegiani, F. A., & Kater, C. E. (2016). Adrenal fatigue does not exist: a systematic review. BMC endocrine disorders, 16(1), 48.
Want to learn more? Have an idea for a blog topic? Reach out!
**I personally recommend these excellent books. If you purchase these books using these links, then I will receive a small commission:
EMDR: If you are working through trauma and considering EMDR, 5 hrs 2 mins. (Link here)
If you want a more clinical approach + self-help tips written by the creator of the modality. 12 hrs 2 mins(Link here)
Panic and Severe Anxiety: If you want a step-by-step structure to help end panic attacks, I’ve seen this book change lives. 6hr 19 mins. (Link here)
General Emotional Intelligence: Simple advice we all need to hear again. 3hr 44 mins. (Link Here)
IFS “Parts work”: If you have an imagination and are ready for deep work, and want to increase self-compassion. 8 hrs 10 mins. (Link Here)
