When the Science Shifts: A Note on SSP and Polyvagal Theory
Informed consent is an ongoing obligation, not a one-time event at the start of therapy. When something relevant shifts in the research informing a practice, sharing that is part of the work. This post is written in that spirit.
What “Why the Polyvagal Theory Is Untenable says”
In February 2026, a paper authored by 39 researchers in autonomic physiology, neuroanatomy, and evolutionary biology was published in Clinical Neuropsychiatry under the title Why the Polyvagal Theory Is Untenable (Grossman et al., 2026 — https://doi.org/10.36131/cnfioritieditore20260110). The researchers — many of whom have been cited in the Polyvagal Theory literature as supporting it — conclude that the theory's core neurobiological premises are not supported by the existing evidence base.
The specific claims under challenge are technical:
whether distinct branches of the vagus nerve uniquely mediate distinct emotional and social states
whether this maps onto a particular evolutionary hierarchy and
whether respiratory sinus arrhythmia reliably reflects vagal tone.
These are mechanistic arguments about how the nervous system works at the level of specific nerve pathways.
In the same journal issue, Dr. Stephen Porges — the originator of Polyvagal Theory — published a detailed response (Porges, 2026 — https://doi.org/10.36131/cnfioritieditore20260111), disputing the characterisation of the theory and defending its foundations. This is an active scientific dispute. It is not a settled verdict in either direction.
What the broader field of knowledge rests on
The therapeutic understanding that our physiology shifts between states — that the body responds to safety and threat, that regulation happens in relationship, that early relational experience shapes the nervous system — does not originate with Polyvagal Theory. It draws on decades of research across multiple independent fields.
John Bowlby's attachment theory established from the 1950s onwards that co-regulation between bodies is not a therapeutic technique but a foundational human need. Allan Schore's work on affect regulation and the neurobiology of early relational experience (1994) mapped these processes independently of PVT. Bessel van der Kolk's The Body Keeps the Score (2014) brought together clinical and neuroscientific evidence for body-level approaches to trauma that extend well beyond any single theoretical framework.
It is also worth acknowledging that knowledge of the body's capacity to settle, mobilise, and connect — and of the role community, rhythm, voice, and relational presence play in that — has been held and practised in Indigenous and ancestral traditions for far longer than it has existed in clinical language. The naming of these processes in neurobiological terms is recent. The knowing is not.
Polyvagal Theory offered one explanatory framework for these observations. That framework is now under serious challenge. The observations themselves have a much wider evidence base.
What this means for SSP specifically
The Safe and Sound Protocol was developed within the Polyvagal Theory framework. It uses filtered music designed to engage auditory pathways associated with the human voice, with the intention of supporting nervous system regulation.
It is important to be precise about what the SSP evidence base actually shows. There are peer-reviewed studies demonstrating functional improvements in auditory processing and sensory responsiveness, primarily in autistic children (Porges et al., 2013 — https://doi.org/10.1016/j.ijpsycho.2012.11.009). Most of this research has been conducted by Porges and affiliated researchers, and the studies are modest in scale. What this research shows is that some people experience measurable functional changes. What it does not resolve — and what this critique makes more pressing — is whether the theoretical explanation for why those changes occur is sound.
That distinction matters. The critique does not claim that SSP produces no effects. It challenges the mechanism proposed to explain those effects. Those are different questions, and conflating them in either direction — either dismissing the intervention or confidently defending it — would not be accurate.
What someone experienced during or after SSP — a shift in how they tolerate sound, a change in how available they feel in relationship, something becoming more accessible — those experiences are their own. They do not stand or fall on whether a particular theoretical model survives scientific scrutiny.
Where things stand, and what this means for you
Sharing this is part of practising ethically. The picture here is genuinely uncertain — not catastrophically so, but more uncertain than it was when SSP was offered as sitting on clearly established neurobiological ground.
I have paused intake for new SSP clients and am currently seeking guidance from my professional association about how this work is best offered going forward in light of this critique.
If you are a past or current SSP client: Your experience is yours and remains real. If you have questions about what this means for your own situation — whether you're mid-protocol, considering a repeat, or simply want to talk through what you're feeling about this — please reach out directly. This is the kind of thing that deserves a conversation, not just a post.
If you were considering SSP: I'm not currently taking new SSP referrals while I seek professional guidance. I'm happy to discuss what other approaches may be relevant in the meantime.
The broader work here — attending to safety, nervous system states, relational presence, and the adaptive nature of distress — continues, and rests on ground that does not depend on Polyvagal Theory being correct.
References
Grossman, P., 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. https://doi.org/10.36131/cnfioritieditore20260110
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. https://doi.org/10.36131/cnfioritieditore20260111
Bowlby, J. (1969). Attachment and Loss, Vol. 1: Attachment. Basic Books.
Schore, A.N. (1994). Affect Regulation and the Origin of the Self: The Neurobiology of Emotional Development. Erlbaum.
van der Kolk, B. (2014). The Body Keeps the Score: Brain, Mind and Body in the Healing of Trauma. Viking.
Porges, S.W., Macellaio, M., Stanfill, S.D., McCue, K., Lewis, G.F., Harden, E.R., Handelman, M., Denver, J., Bazhenova, O.V., & Heilman, K.J. (2013). Respiratory sinus arrhythmia and auditory processing in autism: Modifiable deficits of an integrated social engagement system. International Journal of Psychophysiology, 88(3), 261–270. https://doi.org/10.1016/j.ijpsycho.2012.11.009
Menakem, R. (2017). My Grandmother's Hands: Racialized Trauma and the Pathway to Mending Our Hearts and Bodies. Central Recovery Press.
Gee, G., Dudgeon, P., Schultz, C., Hart, A., & Kelly, K. (2014). Social and emotional wellbeing and mental health: An Aboriginal perspective. In P. Dudgeon, H. Milroy, & R. Walker (Eds.), Working Together: Aboriginal and Torres Strait Islander Mental Health and Wellbeing Principles and Practice (2nd ed.). Commonwealth of Australia.
Related Resources
IMPORTANT INFORMATION
This post is written to meet the ongoing informed consent obligations of ethical therapeutic practice. It describes a published, peer-reviewed critique of the neurobiological framework underpinning the Safe and Sound Protocol, and explains how that critique is being responded to here. It does not constitute clinical advice and is not a substitute for a direct conversation with your therapist about what this means for your own work. Sources are cited throughout and readers are encouraged to follow them and form their own view.
