4/2 Scientific Debate: Polyvagal Theory, the Autonomic Nervous System, and What Happens When a Useful Framework Gets Challenged
- Devon Tonneson
- Mar 31
- 4 min read
If you've spent any time in neurodivergent, trauma, or therapy spaces, you've probably encountered polyvagal theory: the idea that your nervous system moves through three hierarchical states.
It's one of the most influential frameworks in trauma therapy, autism research, and neurodivergent community spaces. It gave a lot of people language for experiences that previously had no name. In February 2026, 39 researchers published a paper in Clinical Neuropsychiatry calling it untenable. Porges responded in the same issue. The debate is very much live.
This week, DNA is doing something a little different. Instead of just reading the science, we're asking what it means when a framework that resonates deeply with lived experience turns out to have contested biological foundations. Science is constantly evolving so its fun to see real scientific debate in real time!
What polyvagal theory actually claims
Porges proposed in 1994 that the autonomic nervous system has three circuits, not two, organized in evolutionary sequence:
Ventral vagal complex: safety, social engagement, calm regulated breathing, facial expression
Sympathetic system: mobilization, fight or flight
Dorsal vagal complex: shutdown, freeze, collapse, immobilization under threat
The theory argues these states are hierarchical: we move down the ladder under threat and back up toward safety with connection and co-regulation. It also claims that the ventral vagal system is uniquely mammalian and underlies social behavior at a physiological level.
What the 2026 paper actually challenges
Grossman and 38 co-signatories published their article in Clinical Neuropsychiatry declaring polyvagal theory "untenable," concluding that its core premises are "not defensible based on existing neurophysiological and evolutionary evidence." This is not a new fight: Grossman first published critiques of polyvagal theory in 2007, with follow-ups in 2016 and 2023, and Porges has responded to each one. Traumatherapistinstitute
The 2026 paper focuses on three specific biological claims:
In plain terms: the critics are saying the anatomy doesn't work the way Porges says it does, and that the measurements used to support the theory may not be measuring what they claim to measure.
What Porges says back
Porges published a point-by-point response in the same journal, arguing that the critics are arguing against things the theory never actually claimed, and that these same misreadings have been showing up and getting corrected in the research for nearly twenty years. Primal Trust
His response evaluates the critique not by disputing individual claims in isolation, but by examining whether the critique engages polyvagal theory as it is actually articulated in the peer-reviewed literature and whether it meets the epistemic standards required for scientific refutation. Clinicalneuropsychiatry
Our Discussion Questions:
What are the five premises Grossman says are wrong, and what does the anatomy actually show? The critique targets specific neuroanatomical claims: that ventral and dorsal vagal regions have unique and separable effects on heart rate, and that this maps onto distinct behavioral states. We'll look at what the actual brainstem evidence says and where the disagreement lives. (Grossman et al., 2026)
Is the "dorsal vagal shutdown" state real? The concept of dorsal vagal shutdown resonates enormously with autistic burnout, dissociation, and freeze states in trauma. Critics argue that the cardiac and neurological mechanisms often attributed to this state may not align with established neurophysiology. If the biological mechanism is wrong, does that change what the state actually is or how we should respond to it? Therapymindbodysoul
What does it mean that Porges responded in the same issue? This debate remains unresolved, leaving clinicians working with models that are experientially useful but theoretically unsettled. We'll ask what it means for a scientific debate to happen in real time like this, and how we're supposed to use frameworks that are still being actively contested. Traumatherapistinstitute
Can something be clinically useful and biologically wrong at the same time? This is the core tension of the session. The critique challenges whether the biology underneath the model is right, but does not address whether the framework has helped people. Neurodivergent communities have used polyvagal language to describe shutdown, safety, and co-regulation in ways that genuinely shifted how they understood themselves. What do we do with that? Substack
Is this about polyvagal theory specifically, or about how neurodivergent communities use science generally? DNA has spent a semester reading papers. This is a good moment to zoom out and ask: how do we evaluate frameworks that give us language for our experiences? What's the difference between a model being useful and a model being true? And when researchers fight publicly over a theory we've built meaning around, how do we hold that?
Design a study that could actually settle this The debate has been running since 2007 with no resolution. What would a study actually need to look like to definitively test the anatomical claims Grossman is making? What's the measurement problem and can it be solved?
Papers we're reading
Grossman, P., et al. (2026). Why the polyvagal theory is untenable: An international expert evaluation of the polyvagal theory. 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).
Porges, S. W. (1995). Orienting in a defensive world: Mammalian modifications of our evolutionary heritage. A polyvagal theory. Psychophysiology, 32(4), 301–318. (the original paper, for context)