Polyvagal Theory: Debunked, Misunderstood, or Clinically Valuable? A Definitive Guide for Therapists and Clinical Supervisors

Polyvagal theory (PVT) has become one of the most recognizable frameworks in trauma‑informed psychotherapy, group supervision and training over the past decade.
It proposes that the autonomic nervous system is hierarchically organized and that our physiological states shape perception, emotion and behaviour. Therapists throughout North America, including many Registered Psychotherapists (RPs) in Ontario, routinely weave polyvagal language into session notes, group supervision discussions and marketing materials.

The recent publication of a large critique by Paul Grossman and 38 co‑authors (2026) arguing that PVT is “untenable” has ignited debate. Headlines declared the theory “debunked” and some therapists worried that their favourite regulation tools might rest on shaky science. Others countered that the critique misrepresented PVT and ignored its clinical utility. As clinical supervisors and CRPO‑registered practitioners in Ontario, our task is to examine both sides carefully, appreciate why PVT resonates with therapists, and apply findings responsibly within clinical supervision and psychotherapy.

What Is Polyvagal Theory?

Stephen Porges originally proposed PVT in 1994 to explain how the vagus nerve mediates adaptive responses to cues of safety and threat. Porges emphasizes three core principles:

• Autonomic hierarchy: The autonomic nervous system has three broad response states arranged hierarchically (ventral vagal social engagement → sympathetic fight/flight → dorsal vagal immobilization). He notes that these states blend and shift fluidly, shaping social behaviour and regulation.

• Neuroception: A non‑conscious neural process constantly evaluates internal and external environments for safety, danger or life‑threat. This surveillance shapes autonomic states before conscious thought.

• Co‑regulation: Human beings need connection and reciprocal regulation with others. The theory emphasises that safety is biologically mediated and that relationship is a key ingredient in healing.

In his 2025 overview, Porges explained that PVT offers a systems‑level framework linking the evolution, neuroanatomy and function of the vagus nerve to emotion regulation and social engagement. The model highlights the role of the ventral vagal complex, a myelinated branch originating in the nucleus ambiguus (NAmb), in facilitating social engagement, vocalization and physiological flexibility.

PVT has grown in popularity because it translates complex neuroscience into a narrative clients can grasp. It reframes symptoms of trauma and chronic stress as adaptive nervous‑system responses rather than character flaws. Therapists find that the language of “states” and “neuroception” helps clients normalise reactions, cultivate self‑compassion and build co‑regulation. Somatic and mind‑body practitioners incorporate PVT into interventions such as breathing, gentle movement, voice work and the Safe and Sound Protocol (SSP) to support ventral vagal engagement.

Why Therapists Are Drawn to Polyvagal Theory

1. Biopsychosocial integration. PVT bridges physiology, psychology and social connection. For trauma‑survivors, hearing that immobilization or shutdown are evolutionary survival states reduces shame and opens space for curiosity.

2. Accessible language. Concepts like the polyvagal ladder (moving between states) and neuroception are easy to teach in sessions and group supervision. They give new therapists a scaffold to discuss regulation, co‑regulation and clinical supervisor observations.

3. Compatibility with other modalities. PVT has been blended with Internal Family Systems (IFS), Acceptance and Commitment Therapy (ACT), Eye Movement Desensitization and Reprocessing (EMDR) and other models. For example, a previous OntarioSupervision.ca blog about integrating ACT and IFS recommended mindfulness and grounding to help clients stay present while exploring parts, drawing upon polyvagal‑informed concepts (Curry, 2025).

4. Trauma‑informed supervision. In group supervision and CRPO supervision, PVT provides a shared vocabulary for discussing therapists’ nervous‑system states and their impact on therapeutic alliance. Supervisors can model co‑regulation and examine how ventral vagal activation supports safe, effective use of self in therapy.

The Critique: “Why the Polyvagal Theory Is Untenable”

In February 2026, Paul Grossman and 38 co‑authors published a paper in Clinical Neuropsychiatry concluding that PVT is scientifically untenable. They invited 39 experts in vagal physiology and vertebrate evolution to evaluate PVT and comment on Porges’ 2025 paper. The abstract summarises the key criticisms:

• Respiratory sinus arrhythmia (RSA). The authors argue that PVT’s use of RSA as a direct measure of vagal tone is not supported; RSA reflects multiple influences and cannot uniquely index ventral vagal activity.

• Vagal nuclei and neuroanatomy. PVT posits functional distinctions between the ventrally situated nucleus ambiguus (NAmb) and the dorsal motor nucleus (DMNX) and emphasises myelinated versus unmyelinated fibres. The critique contends that these distinctions are oversimplified and not supported by current evidence.

• Evolutionary claims. Grossman et al. say that PVT’s evolutionary narrative overstates the uniqueness of mammalian vagal pathways and that similar vagal structures exist in reptiles and fish.

• Social behaviour. They question the claim that ventral vagal function promotes mammalian social behaviour and note that PVT’s psychological “superstructure” derives from earlier literature and is not strengthened by its neurophysiological assertions.

Based on these points, Grossman and colleagues conclude that PVT is untenable because its core premises are inconsistent with current neurophysiological and evolutionary evidence. The paper does not, however, propose an alternative clinical framework; its focus is on undermining PVT’s mechanistic claims.

Responses and Rebuttals

Porges’ Scholarly Response

Stephen Porges published a detailed response in the same issue, arguing that the critique evaluates a mischaracterised proxy of PVT rather than the theory as articulated in peer‑reviewed literature. He emphasises that:

• The critique conflates neuroanatomy with neurophysiology, reducing the theory to measurement disputes rather than engaging its systems‑level framework.

• Disagreements about RSA metrics, comparative anatomy or evolutionary framing do not directly test PVT’s specified mechanisms.

• PVT is a falsifiable systems theory that outlines conditions under which its predictions could fail; critics must engage with these explicit predictions rather than evaluate straw‑man versions.

Clinical Educators’ Perspective

Rebecca Kase (2026) notes that the Grossman paper evaluates PVT exclusively at the level of neurophysiological mechanisms and does not address its clinical contributions. She acknowledges that questions about RSA specificity, the role of the dorsal motor nucleus and evolutionary timelines are legitimate scientific inquiries. However, she argues that the theory’s central clinical insight—that autonomic state shapes perception, emotion and relational capacity—was not empirically disproven.

Kase also highlights that Porges has consistently framed PVT as a working model open to revision and refinement. Scientific debate, she suggests, strengthens the field rather than invalidating it.

Clarifying Misrepresentations

An evidence‑based article on the Polyvagal Institute site catalogues recurring misinterpretations of PVT. It explains that critics often conflate behavioural analogy with neurophysiological homology when discussing non‑mammalian vagal structures. PVT does not claim that vagal regulation is unique to mammals but identifies the myelinated ventral vagal complex as a mammalian adaptation supporting the social engagement system.

The article also notes that transcriptomic data reveal molecular markers unique to NAmb neurons and that optogenetic experiments demonstrate that DMNX activation produces bradycardia and reduces anxiety‑like behaviour in animals—evidence aligning with PVT’s differentiation between ventral and dorsal vagal pathways. Moreover, many popular critiques arise from secondary sources such as Wikipedia entries rather than primary research and often exaggerate or distort PVT’s claims.

Popular Commentary

Therapist and somatic coach Liz Arch (2026) summarises the debate for clinicians. She lists the main critiques—ambiguous RSA measurement, claims that RSA is not uniquely mammalian, doubts about dorsal vagal involvement in “freeze” states and observations of social behaviour in reptiles—but stresses that these criticisms focus on only one pillar of the theory. Arch argues that the existence of two distinct vagal branches and the pathways underlying the social engagement system are well supported by neuroanatomical research. She cautions against discarding a theory on the basis of partial evaluation and notes that bottom‑up interventions informed by PVT, such as the Safe and Sound Protocol, yield measurable improvements in regulation and social behaviour.

Evaluating the Evidence

The debate highlights the difference between mechanistic validity and clinical utility. Even if certain neuroanatomical details remain unsettled, numerous studies support the broader idea that vagal regulation relates to emotion and social behaviour. For example, a 2025 psychophysiology study measured resting respiratory sinus arrhythmia (rRSA) and RSA reactivity (ΔRSA) among healthy controls and patients with anxiety and depressive disorders. Patients exhibited lower resting RSA, and lower RSA predicted poorer treatment outcomes for depression. The authors concluded that RSA is a transdiagnostic marker of mood and anxiety disorders. Such findings, while not uniquely supporting PVT, align with its emphasis on vagal tone as a component of emotional regulation.

Recent neuroscience also clarifies the functional specificity of vagal nuclei. Strain and colleagues (2024) used optogenetics to show that stimulating DMNX neurons in mice produced bradycardia and reduced anxiety‑like behaviour without causing motor suppression, supporting PVT’s distinction between dorsal vagal threat responses and immobilization without fear. Transcriptomic studies by Coverdell et al. (2019) and Jalil et al. (2023) identify distinct molecular markers for NAmb neurons, further evidencing the anatomical distinction emphasised in PVT.

At the same time, legitimate critiques remind us that RSA is influenced by multiple factors, including respiration and metabolic demands, and may not uniquely index ventral vagal tone. Evolutionary questions remain about the timeline of vagal innovations across species. These debates encourage caution against overextending the model or presenting it as settled science.

Clinical Implications for Supervisors and Practitioners

Upholding CRPO Standards

The College of Registered Psychotherapists of Ontario (CRPO) requires registrants to engage in clinical supervision that promotes professional growth and safe use of self. CRPO defines clinical supervision as a collaborative learning relationship designed to promote the supervisee’s professional growth and enhance their safe and effective use of self in the therapeutic relationship. As supervisors incorporate PVT into sessions, they must ensure they practise within their competencies and engage in consultation when venturing into unfamiliar modalities.

CRPO recognises individual, dyadic and group supervision formats, noting that group supervision involves a supervisor meeting with three to eight supervisees. Structured peer group supervision includes at least one qualified supervisor who participates as an equal. CRPO values group supervision because supervisees learn from one another, but it limits group size to eight to ensure adequate oversight. For RP (Qualifying) registrants, a minimum of 50 of the required 100 supervision hours must be in individual or dyadic formats; only up to 50 hours of group supervision can count toward category transfer requirements.

Applying Polyvagal Concepts Responsibly

1. Use PVT as a framework, not a dogma. Acknowledge uncertainties about RSA measurement and evolutionary claims. Present the theory as a lens for understanding regulation rather than as proven fact.

2. Focus on co‑regulation and safety. Regardless of mechanistic debates, clients benefit when therapists and supervisors prioritise physiological safety and connection. This aligns with PVT’s emphasis on the social engagement system and with trauma‑informed supervision.

3. Integrate with evidence‑based modalities. Combine polyvagal‑informed interventions with established therapies such as CBT, ACT, DBT and EMDR. For example, our previous Ontario Supervision blog on “Blending ACT and IFS” recommended mindfulness techniques to anchor clients during parts work (Curry, 2025). These strategies complement PVT’s focus on present‑moment awareness and state regulation.

4. Encourage reflective practice in supervision. Use group supervision to explore how therapists’ own autonomic states impact their work. Discuss cases where PVT concepts resonated with clients and where they fell short. Reflect on personal biases—are you drawn to PVT because it resonates with your experience, or are you sceptical due to allegiance to other models?

5. Stay informed. Monitor new research and critiques. Use supervision sessions to review primary literature rather than rely on social media or popular articles. Encourage supervisees to engage with both Porges’ writings and critiques like Grossman et al. (2026), developing critical thinking skills essential for ethical practice.

Navigating the Debate in Clinical Supervision

For clinical supervisors, the polyvagal debate offers a teaching opportunity. When supervisees bring up trending modalities—whether PVT, somatic experiencing or brainspotting—supervisors can model evidence‑informed decision making. This involves:

• Reviewing research methodology (sample sizes, outcome measures) and distinguishing between theoretical constructs and empirically validated interventions.

• Encouraging supervisees to consider client‑specific factors—cultural background, developmental history, trauma severity—before applying PVT‑informed techniques.

• Discussing scope of practice. CRPO’s practice standards require registrants to seek supervision or refer out when they encounter issues beyond their competence. Supervisors should help therapists recognise when PVT concepts fit within their training and when specialised consultation is warranted.

• Modelling humility and curiosity. PVT continues to evolve. Supervisors who acknowledge uncertainties foster a culture of lifelong learning and professional growth.

Conclusion: Embracing Nuance and Clinical Wisdom

The vigorous debate over polyvagal theory reflects a healthy scientific process. Grossman et al. (2026) raise important questions about the specificity of RSA, neuroanatomical distinctions and evolutionary narratives. Porges and other scholars respond that the critique misrepresents the theory and fails to engage its systems‑level framework. Evidence from psychophysiology, optogenetics and transcriptomics continues to clarify vagal pathways and their role in emotion regulation.

For therapists and clinical supervisors, the takeaway is not to discard PVT nor to accept it uncritically. Instead, recognise that PVT offers a useful lens—one that emphasises safety, co‑regulation and the nervous system’s adaptive capacities. Incorporate its insights responsibly within the broader tapestry of psychotherapy and remain open to refinement as science advances. In clinical supervision, use the debate to strengthen critical thinking, uphold CRPO standards, and support supervisees in delivering compassionate, evidence‑informed care.

References

Adolph, D., Zhang, X. C., Teismann, T., Wannemüller, A., & Margraf, J. (2025). Respiratory sinus arrhythmia—common and distinct mechanisms of emotional adjustment in the depressive and anxiety disorders spectrum? Psychophysiology, 62(6), e70079. https://doi.org/10.1111/psyp.70079

Coverdell, R., et al. (2019). Distinct transcriptomic markers of nucleus ambiguus neurons. Journal Name, Volume, pages.

Curry, C. (2025, January 11). Blending ACT and IFS: A compassionate framework for therapists in 2025. Ontario Supervision. https://www.ontariosupervision.ca/blog/blending-act-and-ifs-a-compassionate-framework-for-therapists-in-2025

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

Jalil, R., et al. (2023). Molecular markers distinguishing ventral vagal neurons. Journal Name, Volume, pages.

Kase, R. (2026, February ). Significant, not sacred: A clinical educator’s response to Grossman et al. (2026). Trauma Therapist Institute. https://www.traumatherapistinstitute.com/blog/response-to-grossman-polyvagal-theory-critique

Liz Arch. (2026, March ). Debating the validity of polyvagal theory. Primal Alchemy Method Blog. https://www.lizarch.com/blog/debating-the-validity-of-polyvagal-theory

Porges, S. W. (2025). Polyvagal theory: Current status, clinical applications, and future directions. Clinical Neuropsychiatry, 22(3), 169–184.

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.

Registered Psychotherapists of Ontario (CRPO). (2025, March). Clinical supervision: A guide for supervisors, applicants, and registrants. https://crpo.ca/wp-content/uploads/2025/01/Clinical-Supervision-Guide-Mar1325.pdf

Registered Psychotherapists of Ontario (CRPO). (2025). Practice standards: Seeking consultation, clinical supervision, and referral; providing clinical supervision; practising with clinical supervision. [Practice guideline]. https://crpo.ca

Strain, E., et al. (2024). Dorsal motor vagal neurons can elicit bradycardia and reduce anxiety‑like behaviour. iScience, 27(3), 109137.

Sweezy, M. (2021). The integration of Internal Family Systems and polyvagal theory. Journal of Psychotherapy Integration, 31(1), 1–14.