How Stress Rewires the Body — and How to Reverse It

Join Dr. James Odell for Season 2 of the Science of Self-Healing Podcast! He's the medical and executive director for BRMI, as well as a practicing naturopathic doctor for over 35 years, and he's here to share with you his extensive knowledge of medicine from a different perspective.

The Bioregulatory Medicine Institute

The Science of Self-Healing Podcast

Stress isn’t just “in your head”—it’s written in your biology.

In this eye-opening episode of The Science of Self-Healing, we explore how the stress response transforms your body and brain, why modern life keeps our nervous systems on high alert, and how trauma imprints itself into our tissues. Moving from amygdala alarms to the quiet power of the vagus nerve, we uncover the hidden chemistry of burnout, anxiety, inflammation, and resilience.

Most importantly, you'll learn how safety, rest, connection, and mindful practices can literally rewire your physiology. If you’ve ever wondered why stress feels so overwhelming—or how healing truly works on a biological level—this episode offers clarity, compassion, and a path forward.

Transcript for: How Stress Rewires the Body — and How to Reverse It

Hello, everyone, and welcome to the Science of Self-Healing podcast. For health and wellness knowledge from a different perspective. Produced by the Bioregulatory Medicine Institute, also known as BRMI. We are your source for unparalleled information about how you can naturally support your body's ability to regulate, adapt, regenerate, and self-heal. I'm your host, Dr. James Odell, the medical and executive director for BRMI, as well as a practicing naturopathic doctor for over 35 years. And remember, this podcast is for informational purposes only and is not intended to be a substitute for the direct care of a qualified health professional who oversees and provides unique and individual care. The information here is to broaden our different perspectives and should not be construed as medical advice or treatment.

Introduction

Hello everyone, and welcome to another episode of the Science of Self-Healing. We often think of stress as something that happens in the mind — that uneasy, restless feeling that creeps up before an exam, a job interview, or a hard conversation. But stress isn’t just psychological. It’s biological. It affects the body’s chemistry in profound ways. When life throws us into chaos — a relationship breakup, a car accident, a financial scare, or even the constant grind of trying to stay afloat — our bodies don’t just react; they transform. Every heartbeat, every hormone, every cell joins the effort to help us survive. But what happens when the crisis never really ends? When the stress response — this ancient, finely tuned system — stays switched on?

Today, we’ll explore the science behind stress and trauma: how they reshape the body and brain, how our biochemistry changes under pressure, and how healing is, in many ways, a physiological process.

The Stress Response in Action

Imagine this: you’re driving late at night when suddenly a deer jumps into the road. Before you even think, your foot slams on the brake, your heart pounds, and your whole-body jolts with energy. That’s the stress response — fast, automatic, and lifesaving.

The Role of the Amygdala and the Fight-or-Flight System

At the heart of it all is a small almond-shaped structure deep in your brain called the amygdala. It acts as your emotional alarm system. The moment it detects danger, it signals the hypothalamus, which then activates the sympathetic nervous system — your body’s accelerator pedal. Almost instantly, the adrenal glands, perched atop your kidneys, release adrenaline and noradrenaline into the bloodstream. Your heart rate spikes. Your breathing quickens. Your blood pressure rises. Glucose rushes into your muscles to give you fuel. Your pupils dilate to take in more light. You’ve entered what’s known as the fight-or-flight state. It’s nature’s way of saying, “Get ready.”

The HPA Axis and Cortisol

A few minutes later, another system kicks in — the HPA axis, short for hypothalamic-pituitary-adrenal. The hypothalamus releases a hormone called CRH, which tells the pituitary gland to release ACTH, which then signals the adrenal glands to secrete cortisol — the body’s primary stress hormone. Cortisol keeps you on alert. It helps maintain blood sugar and blood pressure. It even suppresses systems you don’t need at the moment, like digestion and reproduction, so your body can devote all its energy to survival. In small doses, this process is brilliant. It’s why our species survived predators, wars, and natural disasters. But here’s the problem: the same system that saves your life during a crisis can slowly destroy it when it never shuts off.

Chronic Stress in the Modern World

Our ancestors experienced stress in short bursts — a hunt, a storm, a confrontation. Once the danger passed, they rested. Their bodies recalibrated. Today, our stressors are different. They’re not lions or lightning strikes; they’re emails, bills, commutes, and uncertainty. They don’t end when the sun goes down. And so, the stress response stays active — quietly, persistently, sometimes for years.

How Cortisol Affects the Body and Brain

When cortisol remains elevated, the chemistry of the body begins to change. Cortisol tells fat cells to store more energy, especially around the abdomen. It raises blood sugar, contributing to insulin resistance. It suppresses the immune system, making us more prone to infections but also more vulnerable to chronic inflammation. In the brain, long-term exposure to cortisol can shrink the hippocampus, the region involved in memory and learning. The amygdala becomes more sensitive, firing off danger signals even when there’s no real threat. And the prefrontal cortex, the part of the brain that helps us plan, focus, and regulate emotions, becomes less active. The result is a body and brain stuck in survival mode. You might notice it as restlessness, fatigue, irritability, or brain fog — the subtle signs of a system working overtime.

The Chemistry of Stress

Let’s zoom in a bit further. When you’re stressed, your body releases not just cortisol and adrenaline, but a whole cocktail of chemicals that affect how you think and feel. Norepinephrine floods your brain, sharpening your attention but also narrowing your focus. That’s useful if you’re escaping danger, but not so great when you’re trying to have a calm conversation or fall asleep. 

At the same time, dopamine — the neurotransmitter that helps you feel motivation and reward — tends to drop. That’s why chronic stress often feels like burnout: you’re running hard but feeling no satisfaction.

Serotonin, the molecule that regulates mood, appetite, and sleep, also dips, which can lead to anxiety or depression. Your immune cells even have cortisol receptors. When they’re exposed to cortisol for too long, they become less responsive, leaving you more vulnerable to illness. Paradoxically, other immune pathways go into overdrive, fueling chronic inflammation — the silent spark behind conditions like heart disease, diabetes, and even Alzheimer’s. This is what scientists sometimes call allostatic load — the wear and tear on the body from being stuck in stress mode. It’s the biological cost of adaptation, and over time, that cost adds up.

Understanding Trauma

Now, let’s talk about trauma — the deeper, longer shadow cast by stress. Trauma isn’t just a memory. It’s the body remembering an experience that was too overwhelming to process at the time. When something shatters your sense of safety — whether it’s an accident, abuse, war, or even years of emotional neglect — the brain and body encode that threat pattern deeply. In trauma, the amygdala becomes like an overactive smoke detector, constantly on guard. The hippocampus, which helps distinguish between past and present, weakens. That’s why someone who’s been through trauma might react to a harmless sound or smell as if they’re back in the moment of danger. Their brain isn’t confused; it’s overprotective. 

Meanwhile, the body mirrors the brain’s state. The heart races. Muscles tense. Breathing becomes shallow. Stress hormones surge. These reactions can happen automatically — sometimes without conscious awareness. Over time, trauma embeds itself not only in the nervous system but in the tissues of the body. It affects digestion, immune function, even posture. Research has linked unresolved trauma to chronic pain syndromes, autoimmune disorders, and heart disease. As psychiatrist Bessel van der Kolk wrote, “the body keeps the score.” That phrase isn’t poetic; it’s literal.

The Body’s Capacity to Heal

But here’s the hopeful part. Just as the body records stress and trauma, it also remembers safety and healing. The brain has an incredible capacity for neuroplasticity — the ability to form new pathways and repair old ones.

When we engage in practices that signal safety to the nervous system, such as mindfulness, slow breathing, or even gentle movement, we’re not just relaxing; we’re rewriting biology. When you take a deep breath, for example, you stimulate the vagus nerve, which runs from the brainstem down through the heart, lungs, and gut. Activating this nerve slows the heart rate, lowers blood pressure, and turns on the parasympathetic nervous system — the “rest and digest” counterpart to fight-or-flight. Over time, regular activation of this system lowers baseline cortisol, boosts serotonin, and reduces inflammation.

Exercise helps too, not just by burning energy but by increasing levels of brain-derived neurotrophic factor, a chemical that promotes growth and resilience in neurons. 

Therapy, particularly trauma-focused methods like EMDR or somatic experiencing, can also help rewire the brain’s stress circuits. These approaches teach the body that it’s safe to feel again — to process emotions instead of suppressing them. 

Even simple habits like connecting with others, getting enough sleep, and spending time in nature have measurable biochemical effects. They increase oxytocin, the hormone associated with bonding and trust, which helps calm the amygdala and promote a sense of belonging. Healing, in this sense, isn’t just psychological — it’s physiological.

Stress in the Modern World

We live in an era where our nervous systems are constantly being hijacked. Notifications, news alerts, social media — they all tap into our brain’s stress circuitry, keeping us on edge. Each ping and vibration triggers a microdose of adrenaline. Each scroll keeps the amygdala just a little bit activated. 

Our ancestors had stress, but they also had downtime — rhythms that balanced activation with rest. We’ve lost much of that rhythm. For many people, there’s no clear boundary between work and home, day and night, danger and safety. The result is a low-grade, constant hum of physiological tension.

The Power of Rest and Reset

This is why practices like meditation, digital detox, or even simple quiet time can feel so powerful — they give the body permission to reset. When you step away from constant stimulation, your cortisol levels begin to fall, your vagus nerve activates, and your body re-enters a state of equilibrium. The irony of our modern world is that the very technologies designed to make life easier often keep our ancient biology in perpetual alarm. Recognizing that — and learning to work with, not against, our physiology — may be one of the most important challenges of our time.

Stress, Adaptation, and Resilience

It’s easy to think of stress and trauma as purely destructive, but that’s not the full story. In small doses, stress actually builds resilience. When we face challenges and recover, the body becomes stronger, more adaptable, and more efficient at returning to balance. This process, known as hormesis, is the biological principle behind exercise, fasting, and even certain types of emotional growth. The key is recovery. Stress without recovery breaks us down; stress with recovery builds us up. Resilience, then, isn’t the absence of stress — it’s the ability to return to baseline. It’s what happens when the HPA axis and the vagus nerve learn to dance together: activation when needed, relaxation when possible. 

People who cultivate resilience — through strong relationships, purpose, movement, and mindfulness — tend to show lower levels of inflammation, better immune function, and greater emotional stability. Their bodies still respond to stress, but they recover faster.

Relearning Safety

At its core, healing from stress and trauma is about teaching the body what safety feels like again. Safety isn’t just the absence of danger. It’s the presence of signals that say, “You can rest now.” It’s the sound of a calm voice, the warmth of human connection, the rhythm of steady breathing. These cues activate the parasympathetic system, quiet the amygdala, and lower cortisol levels. 

Polyvagal theory — developed by neuroscientist Stephen Porges — explains this in beautiful detail. It describes how the vagus nerve connects our emotional and physical states. When we feel socially connected and supported, our physiology literally changes: heart rate variability improves, digestion normalizes, and our brains shift from vigilance to curiosity. This is why therapy, support groups, or simply spending time with people who make us feel safe can be so transformative. They aren’t just “nice things to do.” They’re biochemical interventions.

A New Perspective on Stress

Understanding stress and trauma through a biological lens helps strip away the shame we often attach to them. If your body is anxious, tired, or reactive, it isn’t broken — it’s doing exactly what it was designed to do. It’s protecting you. It just needs help remembering that the danger has passed. That’s what healing really is: teaching the body that it’s safe again. It’s not instant. The same way stress changes us over time, so does recovery. Each moment of rest, each act of compassion, each deep breath is a small recalibration — a message to your nervous system that it can trust the world again.

Closing Reflections

So, the next time you feel overwhelmed or exhausted, try seeing your body not as an obstacle but as an ally. It’s working hard to keep you alive, to keep you safe. What it needs most is reassurance — in the form of movement, stillness, connection, or care. 

Stress and trauma are universal experiences. They remind us that we are living organisms — sensitive, adaptive, and deeply interconnected. They show how tightly woven the mind and body really are. 

When we understand that our emotional pain has a physical language — a heartbeat, a breath, a flood of hormones — we start to see healing not as a vague concept but as a measurable, biological process. 

Our bodies are storytellers. They carry the echoes of every moment we’ve endured — but they also carry the potential for renewal. Every time you choose rest over rush, every time you breathe deeply, or reach out to someone you trust, you’re sending a biochemical message of safety through your system. You’re rewriting the story your body tells itself. And that’s where resilience begins — not in the absence of hardship, but in the body’s quiet, tireless capacity to find balance again. 

If this episode resonated with you, share it with someone who might need a reminder that stress and trauma aren’t just stories in the mind — they’re experiences written in the body, and the body knows how to heal. 

Well, that’s all for this episode. Please tune in in two weeks for another Science of Self-Healing. Be Well.

Thank you for your time today, and remember that this podcast is made possible by the Bioregulatory Medicine Institute, also known as BRMI, a nonprofit, global, non political, non commercial institute to promote the science and art of bioregulatory medicine. We extend our gratitude to each and every one of you for listening today, and if you haven't already, make sure to visit us at brmi.online. A treasure trove of invaluable information awaits you there. Connect with us across various social media platforms as well. Come and become a member of our thriving tribe. If you've enjoyed today's episode, we invite you to show your support by rating us, leaving us a review, or sharing the podcast within your circle. Our podcast and mission flourish through sharing, and your participation means the world to us. Our organization is sustained by donations, each of which is tax deductible and fuels projects like this. Visit our website, brmi.online, to contribute or simply to explore the wealth of uncensored and impartial information we offer. No contribution is too small. In just two weeks, we'll be back delving into another captivating topic. Until then, we thank you once again for listening. May wellness and wisdom be your path. Be well.

Bioregulatory medicine is a total body (and mind) approach to health and healing that aims to help facilitate and restore natural human biological processes. It is a proven, safe, gentle, highly effective, drugless, and side-effect-free medical model designed to naturally support the body to regulate, adapt, regenerate, and self-heal. BRMI is a non-commercial 501(c)(3) foundation and will expand and flourish with your support. Our goal is to make bioregulatory medicine a household term.

This article is for informational purposes only and is not intended to be a substitute for the direct care of a qualified health practitioner who oversees and provides unique and individualized care. The information provided here is to broaden our different perspectives and should not be construed as medical advice, diagnosis, or treatment.