Understanding Polyvagal Theory: Why Nervous System Flexibility Matters

An overview of Polyvagal Theory and nervous system regulation, including fight, flight, fawn, freeze, and the window of tolerance (visual created by Dr. Katie Carhart; adapted from work by Stephen Porges and Deb Dana).

Note: Science is always evolving. Since this article was originally written, a recent scientific critique of Polyvagal Theory has raised questions about some of the specific biological claims made in the original model, particularly the idea that emotional states can be mapped onto distinct “ventral” and “dorsal” vagal pathways. While the debate continues in neuroscience, the broader understanding that our nervous system shifts between states of activation, regulation, and shutdown in response to perceived safety or threat remains well supported in trauma research. This article has been updated to reflect the current scientific discussion.

Polyvagal theory offers a powerful framework for understanding how our nervous systems respond to safety, stress, and threat. Rather than viewing anxiety, shutdown, or irritability as personal shortcomings, this approach helps us understand these reactions as adaptive nervous system responses shaped by experience, context, and history (such as trauma).

At its core, polyvagal theory reminds us that the nervous system is always working to protect us. The goal of nervous system regulation is not to stay calm all the time: it is to build flexibility: the ability to move between states and return to safety and connection when possible.

A Brief Overview of Polyvagal Theory

Our nervous system shifts between different patterns of activation depending on whether we perceive safety or threat. Polyvagal Theory has often been used as a framework to describe these patterns.

Three commonly observed nervous system responses include:

Regulated or connected state: a state of presence, engagement, and connection where the body is able to rest, think clearly, and interact with others.

Activation (fight, flight, or fawn): mobilization for action when the nervous system detects threat or challenge. This state may involve increased energy, alertness, and readiness to respond.

Shutdown or immobilization (freeze): a state of reduced energy or withdrawal that can occur when the nervous system perceives threat and action feels difficult or impossible.

We move in and out of these responses throughout the day. This movement is normal and necessary. Difficulties tend to arise when stress, trauma, or chronic overwhelm reduce our ability to move flexibly between these patterns.

When Nervous System Flexibility Is Limited

When the nervous system becomes stuck in activation or shutdown, our ability to function can be impacted in meaningful ways.

Sympathetic Activation in Daily Life

In sympathetic states (fight, flight, or fawn), the body is oriented toward survival rather than connection. This can show up as:

• Snapping at a partner or children

• Feeling easily overwhelmed or irritable

• Reacting strongly to minor stressors

• Restlessness, anxiety, or urgency

• Difficulty slowing down or thinking clearly

These reactions are not character flaws, they are signals of nervous system activation.

Why Awareness Makes a Difference

One of the most effective ways to support nervous system regulation is through early awareness.

When we notice the first signs of activation, such as muscle tension, shallow breathing, racing thoughts, or a sense of urgency, we have more options. Awareness creates space to pause, respond intentionally, and choose regulation strategies before reactions escalate.

Even if we do move fully into a stress state, recognizing it sooner can reduce shame and increase compassion. Instead of asking “What’s wrong with me?” we can shift to “My nervous system is activated right now: what might help?”

Regulation Is About Recovery, Not Perfection

Being regulated does not mean never getting dysregulated. It means:

• Noticing stress sooner

• Recovering more quickly

• Having tools that support regulation

• Repairing after moments of disconnection

This ability to move between states and return to safety is often described as the window of tolerance. Expanding this window takes time, practice, and support, especially for those with a history of trauma or chronic stress.

Nervous System Capacity Matters

Polyvagal theory also helps us understand why change can feel difficult at times.

When someone is in a dorsal vagal (freeze or shutdown) state, the nervous system may not have the capacity to take in new information, try new skills, or make decisions. In those moments, offering strategies or solutions often doesn’t land, not because someone isn’t trying, but because their system is prioritizing survival.

Understanding nervous system capacity allows for a more compassionate and effective approach to healing.

Working With Your Nervous System, Not Against It

Polyvagal theory invites a different question:

What does my nervous system need right now?

Sometimes the answer is movement or action. Sometimes it’s rest, connection, or simply noticing what’s happening in the body. Healing and regulation happen most effectively when we work with the nervous system rather than pushing past its limits.

Limits of Polyvagal Theory

It’s also important to note that Polyvagal Theory includes a mix of well-established autonomic physiology and theoretical elements that continue to be debated in the scientific literature. While the theory has been influential in trauma-informed care, some of its specific anatomical and evolutionary claims, particularly the idea that emotional states map onto distinct “ventral” and “dorsal” vagal pathways, have been questioned by researchers.

In 2026, a group of neuroscientists and psychophysiology researchers published a critique arguing that several of the theory’s proposed biological mechanisms are not strongly supported by current empirical evidence.¹ These critiques focus primarily on the theory’s neuroanatomical and evolutionary explanations rather than on the broader observation that nervous system states influence how we think, feel, and respond to stress. After it came out, I saw many posts on social media using language like "RIP Polyvagal Theory," and I truly don't believe that is an accurate take-away.

Scientific debate like this is a normal part of how knowledge evolves. Theories are continually tested, refined, and updated as new research emerges. Acknowledging the limits of a model does not mean the clinical observations associated with it are invalid.

In practice, many clinicians use polyvagal-informed ideas as a framework for understanding patterns of nervous system activation, regulation, and shutdown. These patterns can help both clinicians and clients recognize when regulation, pacing, or additional support may be needed before deeper processing or skill-building can occur.

How Polyvagal-Informed Perspectives Can Inform Therapy

Understanding nervous system capacity is an important part of trauma-informed therapy. When a person’s nervous system is in a state of high activation or shutdown, their ability to process information, reflect, or try new skills may be temporarily limited.

For example, when someone is experiencing a shutdown or immobilization response, offering new coping strategies or tools may not be helpful in that moment, not because the client is resistant or unmotivated, but because their nervous system does not yet have the capacity to take in or apply new information.

Recognizing patterns of activation, regulation, or shutdown allows therapy to meet clients where they are. In many cases, this means prioritizing safety, stabilization, and regulation before attempting deeper emotional processing or introducing new skills.

As nervous system capacity increases, learning, reflection, and skill-building often become more accessible.

Key Takeaways: How I Think About Polyvagal Theory

After reviewing the recent critiques and responses, here’s where I currently stand.

Some of the specific biological explanations proposed in Polyvagal Theory, particularly the idea that emotional states map onto distinct branches of the vagus nerve, do not currently have strong empirical support and remain debated within neuroscience.

At the same time, much of the framework draws on well-established research about the autonomic nervous system and how our bodies respond to safety and threat. Decades of trauma research support the idea that changes in nervous system activation influence how we think, feel, and behave.

For many clinicians, Polyvagal Theory has provided a helpful way to organize and communicate these patterns. In practice, it can:

• Help clients understand common stress and trauma responses in ways that reduce shame and self-blame.

• Give clinicians a framework for recognizing when someone is activated, regulated, or shut down.

• Encourage therapy to be paced according to a person’s nervous system capacity, rather than pushing for change when the system is overwhelmed.

In this sense, the value of the framework does not depend on every proposed biological mechanism being correct. As research continues to evolve, many clinicians are adjusting how we talk about the underlying physiology while continuing to use the broader insights about nervous system regulation to guide trauma-informed care.

To me, this is science working as it should. In psychology and neuroscience, theories are continually tested, debated, and refined as new evidence emerges. Over time, this process helps strengthen our understanding and improve how we apply research in clinical practice. Ultimately, the goal is not to apply a theory perfectly, but to help people better understand their bodies and develop greater flexibility in responding to stress.

Interested in Working Together?

I integrate polyvagal-informed, trauma-informed approaches into therapy to support nervous system regulation, emotional awareness, and sustainable change. Together, we focus on building flexibility, expanding the window of tolerance, and responding to stress in ways that feel supportive rather than overwhelming.

If you’re curious about how this approach might support you, you can learn more about working with me here or reach out to schedule a consultation.

About the Author

Dr. Katie Carhart, PhD is a licensed clinical psychologist and founder of Align & Empower Therapy. She specializes in trauma-informed therapy, adult ADHD evaluation and neurodivergent-affirming care, burnout, and nervous system regulation.

Further Reading

These sources represent the ongoing scientific conversation about Polyvagal Theory. As with many areas of psychology and neuroscience, research continues to evolve.

Core Debate

1. Grossman et al. critique

Grossman, P., et al. (2026).Why the Polyvagal Theory Is Untenable: An international expert evaluation of the Polyvagal Theory. Clinical Neuropsychiatry.

This paper argues that key physiological and evolutionary claims of Polyvagal Theory are not supported by current evidence.

2. Porges’ response

Stephen W. Porges (2026).When a Critique Becomes Untenable: A Scholarly Response to Grossman et al.’s Evaluation of Polyvagal Theory.Clinical Neuropsychiatry.

Porges argues the critique evaluates a misrepresented version of the theory and does not accurately engage the model as described in the literature.

Polyvagal Theory Research Overview

3. Porges overview paper

Porges, S. W. (2025).Polyvagal Theory: Current Status, Clinical Applications, and Future Directions. Clinical Neuropsychiatry.

This article summarizes the theoretical foundations and proposed clinical implications of Polyvagal Theory.

Clinical Translation

4. Deb Dana

Dana, D. (2018).The Polyvagal Theory in Therapy: Engaging the Rhythm of Regulation.

This book translates polyvagal concepts into practical tools clinicians can use to support regulation and safety in therapy.