Stephen Porges Is Still in the Question. So Should We Be.

In September 2025, Stephen Porges published a peer-reviewed paper in Frontiers in Behavioral Neuroscience titled "Polyvagal theory: a journey from physiological observation to neural innervation and clinical insight." It is thirty years in the making and it belongs in the clinical conversation.

This is not a newsletter response or a public statement. It is a full empirical and theoretical paper incorporating new transcriptomic research, neurophysiological evidence, and direct engagement with the critiques that have been circulating in the field. For clinicians who have been tracking the debate around polyvagal theory, this paper matters. And for those who have not yet engaged with that debate, it is a useful place to start.

I want to offer three things this paper clarifies, because I think they are worth sitting with regardless of where you land on the broader scientific conversation.

The debate is about neuroanatomical precision, not clinical irrelevance.

This distinction is important and it is frequently lost in how the debate gets summarized. The critiques of polyvagal theory, most notably the 2025 paper by Grossman and colleagues published in Clinical Neuropsychiatry, raise questions about specific neuroanatomical and methodological claims within the theory. They are not claiming that nervous system regulation is irrelevant to trauma treatment, that safety is unimportant in clinical settings, or that the clinical applications built around polyvagal frameworks have no value.

Porges addresses this directly. The theory has been iteratively refined over thirty years precisely because it was built to integrate new evidence rather than resist it. What is being debated is the precision of the underlying model, not the validity of the clinical and therapeutic observations that informed it.

For clinicians, this matters because it changes how we hold the framework. Not as a belief system to defend, but as a working model to engage with honestly, including its uncertainties.

RSA is not a metaphor. It is a measurable neurophysiological signal.

One of the most valuable contributions of this paper for clinicians is its detailed explanation of respiratory sinus arrhythmia, what it actually is, where it originates, and why it has clinical relevance.

RSA is the rhythmic fluctuation in heart rate linked to the respiratory cycle. It is a measurable output of myelinated vagal efferents originating in the nucleus ambiguus, the brainstem structure at the core of the ventral vagal complex. When we observe someone settling into safety in a clinical session, when we notice the quality of breath change, the voice soften, the eyes become more available, RSA is part of what is shifting in real time in the body. That is not pop science. It is documented neuroscience, and this paper lays out the neuroanatomical and methodological evidence with considerable rigor.

Porges also introduces the concept of vagal efficiency, a dynamic measure of how effectively the ventral vagal pathway adjusts cardiac output in response to changing demands. This level of specificity is exactly what separates clinically grounded nervous system work from the kind of vague, metaphor-heavy content that has become increasingly common in wellness spaces. Understanding what we are actually observing when we observe regulation, even imperfectly, makes us better clinicians.

Thirty years of iterative science is itself a lesson.

What I find most meaningful about this paper is not any single finding. It is the story it tells about how knowledge actually develops.

Porges began observing beat-to-beat changes in heart rate variability as a graduate student in the late 1960s. What he noticed was dismissed as noise. The field at the time was not interested in individual variation. It wanted group effects, clean causal lines, and reproducible averages. He spent decades developing the methodological tools necessary to extract a meaningful neural signal from what everyone else was calling statistical error.

Polyvagal theory did not arrive fully formed. It was built incrementally, revised in response to new evidence, situated within evolving neuroanatomical knowledge, and is still being refined today. The paper traces this arc explicitly, from his early HRV research in newborns to the development of the Porges-Bohrer method to the most recent transcriptomic evidence about the molecular specialization of the mammalian ventral vagal complex.

That is what rigorous science looks like. Not certainty delivered from a podium. Not a framework that claims to have answered every question before the questions have been fully asked. Iterative, honest, sometimes slow, and always accountable to the data.

I think about this in clinical work too. The frameworks we use, polyvagal theory among them, are not destinations. They are working models. They help us ask better questions about what is happening in the nervous system and what conditions support regulation, safety, and healing. When those models are challenged, the right response is not to defend them as though they are scripture or abandon them as though they are fraudulent. It is to stay in the question with the same rigor and curiosity the science itself demands.

The people doing this field well have always known this. The map is not the territory. The framework is not the healing. The theory is not the nervous system itself.

Porges is still in the question. Thirty years in, peer-reviewed, precise, and intellectually honest. That is the standard worth holding.

The full paper is available at Frontiers in Behavioral Neuroscience and is linked below. It is open access and worth reading directly.

Porges, S.W. (2025). Polyvagal theory: a journey from physiological observation to neural innervation and clinical insight. Frontiers in Behavioral Neuroscience. https://doi.org/10.3389/fnbeh.2025.1659083

With you in the work, Christina

Christina Hull, MSW, LCSW Trauma Therapist | Educator | Founder, Sage and Soothe Wellness christinalhull.com