What Does the Scientific Debate on Polyvagal Theory Mean?

‍ This is a companion piece/update to an earlier post, Why Is Polyvagal Theory Important to Yoga?

Do you remember the questions posed at the start of that earlier post? Do you feel calm, trusting, connected, part of a community? Or do you tend toward agitation, always ready for a fight or a flight? Or toward numbness, shutdown, a sense of being alone even in a room full of people? Those questions still matter. The nervous system patterns behind them are still real, still observable, and still central to why we teach yoga the way we do at YogaX. What has changed is the scientific conversation swirling around the framework we have long used to describe those patterns: polyvagal theory (PVT). This blog explores what the scientific debate on PVT means and does not mean for yoga, therapeutic yoga, and yoga therapy.

Why an Update, and Why Now?

In early 2026, a group of 39 physiologists and evolutionary biologists, led by researcher Paul Grossman, published a detailed critique arguing that several of the physiological and evolutionary claims underlying polyvagal theory do not hold up against current evidence. Stephen Porges, the originator of the theory, published an equally detailed rebuttal in response. Both papers are long, technical, and, frankly, a bit combative in tone. Neither is required reading for most of you. But because some of this debate has made its way into podcasts, social media, and even a few training programs framing it as “polyvagal theory has been debunked,” it feels important to offer our own community a clear and grounded take.

Here is the short version: the critique raises legitimate points about specific physiological and evolutionary claims. It does not undo the clinical value of the framework. The rest of this post explains why and what we are adjusting in how we talk about polyvagal theory and polyvagal states.

What Still Holds Up

The heart of polyvagal theory, and the reason it has become so useful in yoga therapy, trauma-informed teaching, and clinical psychology alike, is a functional idea: the state of your nervous system shapes what you perceive, feel, and are capable of doing. When you feel physiologically settled, you have access to connection, reflection, and flexibility. When you feel mobilized, your attention narrows toward threat and action. When you feel overwhelmed, your system may shift toward withdrawal and disconnection, even collapse.

This is not a controversial claim, and none of the recent critique touches it. It is observable in the therapy room, on the yoga mat, and in ordinary life. It is supported broadly by affective neuroscience, psychology, and even yoga traditions beyond polyvagal theory specifically. And it remains, in our view, the most useful thing the theory offers: a shared language for recognizing that regulation is physiological and not merely psychological, that behavior is often state-dependent and autonomically driven rather than simply willful, and that connection with others has a biological foundation as well as a relational one.

This same three-part pattern, engaged, mobilized, or shut down, also showed up independently in the trauma field around the same time PVT was taking shape. Peter Levine's foundational book Waking the Tiger (1997), built on ethology and the study of stress physiology rather than on vagal anatomy, describes a strikingly similar pattern of engagement, mobilization, and freeze in response to threat. Two independent lines of work landing on the same functional pattern is exactly the kind of convergence that gives a clinical framework real staying power, regardless of how its underlying mechanism eventually gets refined.

What Is Being Refined

Where the critique has teeth is in some of the more specific mechanistic claims that have often been taught, including by us, as settled fact.

First, the critique correctly points out that heart rate variability (HRV), the measure many of you already track through a wearable, an app, or a biofeedback session, is not a clean, direct readout of vagal tone. Much of what shows up as HRV is closely tied to the natural speeding and slowing of heart rate with the breath, a phenomenon researchers have long called respiratory sinus arrhythmia, or RSA (some now prefer the term respiratory heart-rate variability, a renaming that matters more to researchers than to the rest of us, and that we mention only so the terms do not trip you up if you encounter them elsewhere). What matters clinically is this: HRV, however it is labeled, is shaped by breathing rate and depth, blood pressure, age, and several other factors, not by vagal activity alone. This does not mean tracking your HRV, or noticing your breath’s effect on it, is meaningless. It means we should describe what it shows with a bit more humility than “this proves your vagal tone is improving.”

Second, one refinement matters even more to how we teach: the idea that ventral vagal and dorsal vagal function as two discrete switches, cleanly flipping a person from one behavioral mode into another, is not well supported. Both branches of the vagus nerve are more anatomically and functionally intertwined than the popular three-state model suggests, and this pattern holds across a wider range of species than the theory originally proposed. In practice, this means a nervous system rarely toggles cleanly from one state to another. Regulation looks less like a light switch with three fixed positions and more like a shifting blend of activation and settling.

Third, one claim in particular deserves attention, because it circulates widely in trauma-informed teaching: the idea that a shutdown or freeze response reflects a literal, massive drop in heart rate driven by the dorsal vagus. The evidence for this specific claim, in humans, is thin. Studies of people experiencing freezing or dissociation generally do not find dramatic, life-threatening drops in heart rate. They may find little change, or a modest decrease that plausibly reflects reduced movement rather than a dramatic parasympathetic event. Interestingly, even Porges’s own recent response to the critique moves toward a softer description of dorsal vagal shutdown, framing it as a shift in regulatory dominance rather than a specific cardiac event. We think that is the right shift. What this point means practically is that the felt experience of shutdown, numbness, collapse, and withdrawal is real, clinically important, and worth taking seriously. Teaching it as a verified, single-pathway cardiac mechanism is not.

Holding the Language as a Map, Not the Territory

Terms such as ventral vagal, sympathetic activation, and dorsal vagal shutdown are useful precisely because they are intuitive. They let teachers and students communicate quickly about a felt pattern. What they are not is a literal, moment-to-moment readout of a specific nerve or set of nerve fibers firing in isolation. I am not proposing that we, or the field, set this language aside. Ventral vagal and dorsal vagal have become part of the working vocabulary of yoga therapy and trauma-informed practice more broadly, and a shared vocabulary has real value even when its underlying science is still being refined. Asking every teacher, therapist, and client to abandon language this ingrained, in favor of something more cautious but less familiar, would cost more in clarity than it would gain in precision. What I am proposing is a shift in how we hold the language, not a shift away from it entirely.

It is helpful to think of polyvagal language the way we think of a map. A map is useful. It orients you, helps you plan a route, helps you communicate with a fellow traveler about where you are. It is not the territory itself, and no one expects it to be, and yet we keep using maps because they work well enough for the purpose at hand. Polyvagal terms can be used the same way: as a shared, well-worn shorthand (or heuristic) for patterns of engagement, mobilization, and withdrawal, retained deliberately for the practical and communicative value it offers, rather than defended as a precise diagram of the brainstem.

This representation, incidentally, is not a new idea in the contemplative traditions we draw from. Yoga has long described human experience through the gunas: sattva (clarity and balance), rajas (activation and movement), and tamas (inertia and withdrawal). These are not fixed states to be achieved or avoided, but qualities that continually shift and combine, as Sullivan et al (2018) described and I have further elucidated (Brems, 2024; 2025). Without forcing an exact one-to-one mapping onto the nervous system, the parallel is hard to miss: regulated and connected states are deeply correlated with sattva, mobilized states with rajas, withdrawn states with tamas. The deeper teaching, in both frameworks, is the same. Wellbeing is not about eliminating these shifts. It is about developing a skillful, resilient relationship with all of them.

What This Means in Practice

Everything in the earlier post about PVT and about how yoga supports regulation still stands: the community and safety cues, the breath as an access point to the nervous system, the movement that helps discharge activation or gently reawaken a numbed system, the mindfulness that lets you notice what is actually happening rather than what you expect to feel. There is no need to retract any of that, and we encourage you to revisit that post for the fuller list of practices.

What is worth refining is the confidence with which we attach specific physiological claims to specific practices, not the vocabulary itself. We may still say a practice “supports a ventral vagal state,” because that phrase does real communicative work for many of you. We are simply holding it, internally and in how we teach it, as shorthand for a felt pattern rather than as a verified singular mechanism. At the same time, we might say “this practice may support a shift toward settling and connection, in part through its effects on breath and the vagus nerve,” when a bit more precision seems called for. Both statements can be true and useful at once. The vocabulary can stay familiar. What shifts is the certainty we quietly attach to some of the anatomical and physiological underpinnings.

Closing Thoughts

Yoga therapy has never required certainty to be effective. It has always asked for attunement, discernment, and the willingness to work with complexity rather than around it. Polyvagal theory, held with appropriate care, continues to offer a valuable language for understanding human experience. The ongoing scientific debate about its finer mechanisms is not a reason to discard that language. It is an invitation to use it more precisely, and with the same humility we try to bring to every other part of this practice.

With gratitude to all who care about the human nervous system, and to all of you who keep asking good questions about it.

Chris

About the Author: Christiane Brems, PhD, ABPP, E-RYT500, C-IAYT, is the Director of YogaX, a clinical psychologist, registered yoga teacher, certified yoga therapist, and certified Buteyko (breathing) instructor. She has practiced yoga for nearly 50 years. You can read more about her on the YogaX Team page and at https://www.christianebrems.com/.

For those who want to go further into the current scientific debate:

For a longer and more detailed ‘sciency’ version of this blog, please contact Chris.

Also check out the following primary readings for yourself:

Grossman, P., Ackland, G. L., Allen, A. M., Berntson, G. G., Booth, L. C., Burghardt, G. M., et al. (2026). Why the polyvagal theory is untenable: An international expert evaluation of the polyvagal theory and commentary upon Porges (2025). Clinical Neuropsychiatry, 23(1), 100–112.

Porges, S. W. (2026). When a critique becomes untenable: A scholarly response to Grossman et al.’s evaluation of Polyvagal Theory. Clinical Neuropsychiatry, 23(1), 113–128.

Menuet, C., Ben-Tal, A., Linossier, A., Allen, A. M., Machado, B. H., Moraes, D. J., et al. (2025). Redefining respiratory sinus arrhythmia as respiratory heart rate variability: An international expert recommendation for terminological clarity. Nature Reviews Cardiology, 22, 978–984.

And, as always, the original recommendations:

Brems, C. (2025). Integrated holistic yoga psychology: Volume 1 in Therapeutic yoga teaching, clinical service, and practice. Integrated Holistic Press.

Brems, C. (2024). Therapeutic breathwork: Clinical science and practice in healthcare and yoga. Springer.

Porges, S. (2017). The pocket guide to the polyvagal theory: The transformative power of feeling safe. Norton.

Dana, D., & Porges, S. (2018). Clinical applications of the polyvagal theory: The emergence of polyvagal-informed therapies. Norton.

Levine, P. A. (1997). Waking the Tiger: Healing Trauma. North Atlantic Books.

Rosenberg, S. (2017). Accessing the healing power of the vagus nerve. North Atlantic Books.

Sullivan, M. B., Erb, M., Schmalzl, L., Moonaz, S., Taylor, J. N., & Porges, S. (2018). Yoga therapy and polyvagal theory: The convergence of traditional wisdom and contemporary neuroscience for self-regulation and resilience. Frontiers in Human Neuroscience, 12:67-82.