Polyvagal Theory debunked in comprehensive new study

A recent paper co-authored by 39 leading scientists names the Polyvagal Theory ‘untenable.’ It’s the work of more than four decades, with agreement from experts in wide-ranging fields. But some in the psychological community are hesitant to let Polyvagal Theory go.

InSight+ spoke with lead researcher Professor Paul Grossman about this latest paper, a lifetime of studying the topic, and why he thinks this truth is important.

Professor Paul Grossman has spent most of his career studying how the autonomic nervous system (ANS) affects the heart during challenging situations, and the last two decades challenging the validity of Polyvagal Theory, one of psychotherapy’s biggest hits.

Professor Grossman is a psychologist and psychophysiologist, and Emeritus Research Director of Psychosomatic Medicine at the University Hospital Basel, Switzerland. His most recent paper, ‘Why the Polyvagal Theory is Untenable,’ co-authored with 38 ANS scholars, was published in Clinical Neuropsychiatry.

The paper debunks key tenets of the Polyvagal Theory from evolutionary and physiological standpoints.

Disconfirming Polyvagal Theory

The Polyvagal Theory was developed by Dr Stephen Porges, PhD, in the mid ‘90s. The Polyvagal Institute describes Polyvagal Theory as ‘through the process of evolution the mammalian ANS [Autonomic Nervous System] has a primary repertoire of 3 principle states:’ ‘Relaxed,’ ‘Immobilised’ and ‘Mobilised.’ The Theory emphasises the role of the Autonomic Nervous System, and in particular the vagus nerve, in regulating the behaviour of mammals, which it says is unique to mammals.

Professor Grossman and his co-authors refute five key premises of the Polyvagal Theory in the recent paper. He spoke to InSight+ from Germany.

“The base of the Polyvagal Theory is that there are two vagal areas in the brainstem: the dorsal vagus — the dorsal motor nucleus in fact — and the ventral area, which is named the nucleus ambiguous,” said Professor Grossman.

“They do exist. And they do have different functions. But they’re not the functions that the Polyvagal Theory mainly attributes to them.”

“Particularly the dorsal vagus nucleus, which predominantly influences control of gut function. There is some influence in the heart, but they are usually minimal or very minimal in most species of mammals tested.”

“Polyvagal Theory confidently asserts quite the opposite, that the dorsal vagus can induce massive and even lethal heart rate slowing under conditions of immobility due to extreme emotional circumstances (eg, emotional freezing).”

“There is absolutely no evidence to support this role of the dorsal vagus, and much to speak against the theory.”

“Respiratory sinus arrhythmia (RSA) is defined as accelerations of heart rate with inspiration, and deceleration with expiration.”

“The vagus — the major nerve of the parasympathetic nervous system — in fact contributes to the how fast the heart beats. Increased vagal impulses from brain to heart serves to slow heart rate.”

“Under normal conditions, we cannot directly measure the vagal activity to the heart, and researchers have relied upon an indirect index to do so. This is the linchpin of the body of research of vagal influences upon heart rate. This phenomenon has been called respiratory sinus arrhythmia; is more appropriately termed respiratory heart-rate variability (rHRV).”

“The polyvagal theory correctly says that the ventral vagus is responsible for rHRV — but so are virtually all vagal influences upon heart rate.”

“Furthermore, rHRV is an imperfect index of the extent of vagal traffic from brain to heart; it’s an approximate measure and subject to many limitations as a measure. Polyvagal Theory, on the other hand, proposes that it is a direct measure of central vagal influences upon the heart, which is clearly false.”

“Additionally, Polyvagal Theory proposes that the dorsal vagus is an evolutionarily primitive, reptilian area that turns on during emotionally defensive situations, such as extreme danger. It posits that the dorsal vagal nucleus is essentially responsible for shutting down the autonomic nervous system during emotional freezing, or dissociation.”

“There are several meta-analyses showing that during the emotional freezing associated with psychological dissociation there is no, or very little, change in heart rate. Certainly not a dramatic increase in bradycardia.”

Professor Grossman says that while shutdown, psychological dissociation, and other positive and negative psychological experiences occur and are genuine physiological events, the best evidence indicates those experiences are not regulated by the ANS alone, but by various brain centres.

Lizards, mammals, and the ventral vagal

Another central idea of the Polyvagal Theory is that the mammalian ventral vagus is evolutionarily advanced, and dorsal vagus represents a ‘left-behind’ reptilian vagus.

“Porges himself used to talk about the “smart” and the “dumb” vagus in the 1990’s,” Professor Grossman said.

“Polyvagal Theory maintains that the ventral vagus in mammals has been “repurposed” to be responsible for positive, affiliative psychological processes including social regulation, safety and co-regulation. And that other vertebrates — for example fishes, reptiles, amphibians and birds — do not show complex social behaviours.”

“Reptiles, particularly, have been depicted as nonreactive emotionally defensive animals, who primarily respond to threat.”

“There is ample evidence of complex social behaviours in nonmammal vertebrates. There is no evidence that the ventral vagus has been repurposed in mammals to facilitate higher-level social processes.”

A career of sharing knowledge

Professor Grossman wrote his first article on relations between breathing, stress, and parasympathetic control of heart rate about 45 years ago, called Breathing to the Heart of the Matter.

“My interest originally focussed upon trying to measure vagal influences on the heart. Early collaborations with physiologists, to this day, have led me to understand what we do and do not know about the parasympathetic and autonomic nervous system in relationship to psychological processes, as well as serious problems assessing vagal activity.”

“I have always understood my own lack of deep knowledge regarding the complexities of autonomic physiology, and I needed to work with experts in the area.”

“For my first critique of Polyvagal Theory in 2007, I sent emails to the very top evolutionary specialists I could find.”

“I asked four of them for reprints of their papers, and whether they’d heard about Polyvagal Theory. Within 24 hours, all four wrote back that they believed the theory was nonsense.”

One of the four was the distinguished scholar of ANS evolution, Edwin W. Taylor, a co-author of the current publication.

“My primary motivation has always been to contribute to improved understanding among psychophysiologists, psychologists and other healthcare professionals.”

“Over-simplified, over-interpreted and erroneous information isn’t helpful for patients, therapists, or disciplines.”

“This paper is not much different than one I wrote in 2023, but it’s better, because it was written together with 38 luminaries. Agreement among us was remarkably easy and unanimous.”

What about the therapies?

Professor Grossman’s conclusion suggests that psychologists, psychiatrists, psychotherapists and allied professionals currently influenced by Polyvagal Theory should reorient and consider other existing, and novel, psychophysiological explanations.

“There’s a relatively sound psychophysiological literature that has more refined, more complex explanations for psychological or physiological responses to stress or emotional freezing.”

“There are certainly physiological processes going on, but maybe we can’t specify what those processes are for individual patients. We’re left with our lived experience of physical sensations and perceptions.”

“Dismissing somatic therapies, or psychotherapy, is not the point. Many of these practices have been around well before the Polyvagal Theory ever became polyvagal informed psychotherapy.”

“There’s a whole area of meditation and relaxation and interventions that have been used for millennia.”

“Physiologists understand that even fight-or-flight cannot be characterized as a purely sympathetic phenomenon. It’s much more complex. There are specific neurons that send specific information to specific organs or muscles, or other processes. There is an integrated system.”

Becca Whitehead is a freelance journalist and health writer. She lives in Naarm and is a regular contributor to the MJA’s InSight+.

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