Happy families are all alike; every unhappy family is unhappy in its own way. I first learned of the vagus nerve through a deeply unhappy married couple I knew (personally, not professionally—I am not a therapist). They used to torment each other with endless “emotional processing” that, it gradually dawned on me, orbited around a few recurring concepts: regulation, dysregulation, coregulation, fawn, freeze, safety, shutdown, and most of all “the nervous system” and its apparent centerpiece the vagus nerve.
These were all unfamiliar to me; even though I’d spent years studying biology I had simply never heard of the vagus nerve as the lynchpin of the nervous system. In these processing sessions, the couple transformed signature feelings of the marital experience like jealousy, resentment, anger, and frustration into physiological—or, more accurately, pseudo-physiological—declarations.
The wife would get angry with the husband for not putting the dishes away when he said he would, but instead of expressing this straightforwardly, she’d spin an impossible tale about how she in fact wasn’t angry, but had had an experience of unsafety at the sub-cognitive level of her “nervous system,” which was now “dysregulated” as a result. The husband would avoid communicating disappointing information (“I’ll be an hour later than usual tonight”) until it was certain to cause frustration and conflict because of how the wife typically reacted to such information. Instead of owning his fear of disapproval, he would explain to her that his anticipation of her disappointment had so dysregulated his “nervous system” as to put him in a state of “fawning.”
It was excruciating to watch two empathetic and emotionally intelligent people chase each other around this track, framing their conscious emotions as physiological nervous system states and never reaching a resolution. As I’ve said, this was unfamiliar to me at the time. Where was it all coming from? I suspected some kind of alternative wellness thing, and I was half right. I eventually learned that both husband and wife had received training in something called the Safe and Sound Protocol.
The Safe and Sound Protocol is the brainchild of Dr. Stephen Porges, an American psychologist and traumatologist who is currently a professor at the University of North Carolina and director of the Traumatic Stress Research Consortium at Indiana University. The protocol was developed based on Porges’s most famous contribution to psychology, his proposed “Polyvagal Theory,” henceforth PVT.
Porges published the first paper outlining his ideas in 1994 while serving as director of the Brain-Body Center at the University of Chicago. There, he proposed a novel role for the cranial vagus nerve in mediating complex social and emotional behavior. The vagus nerve was already known to be a major component of the autonomic nervous system, which regulates involuntary body functions like heartbeat, breathing, swallowing, and fainting. What Porges suggested was that, basically, the vagus nerve is the mind-body connection. From there, the theory took off to visit some truly strange climes.
Polyvagal Theory is so named because of its central claim about the neurophysiological basis of emotion. According to the website for Porges’s Polyvagal Institute (established 2020), the vagus nerve has multiple distinct anatomical and functional components (hence “polyvagal”) that correspond to an evolutionary “hierarchy” of autonomic nervous system states.
A few notes about terminology here. The autonomic nervous system is the part of the nervous system that controls involuntary processes of the body, like breathing and digestion. It is commonly divided into two sub-systems, the “fight or flight” or sympathetic sub-system and the “rest and digest” or parasympathetic sub-system. In terms of the word “hierarchy,” the Polyvagal Institute website is careful to note that this hierarchy is purely evolutionary (that is, not normative): “[evolutionarily] newer circuits support social engagement and flexible regulation, while older circuits support more fundamental defensive strategies… as conditions become more challenging, regulation may move from newer, more flexible circuits to older, more fundamental [primitive] ones.” That is, it’s not that more regulated states are better, it’s that they’re newer and more complex; when you’re stressed or threatened, your “nervous system” will revert to more primitive, less complicated mechanisms to keep itself working.
This, the central theoretical insight of PVT, rests on a bewildering jumble of physiological and anatomical claims about the human nervous system. In particular, PVT is unique in claiming that the vagus nerve itself has two components that are both anatomically and functionally distinct. The first “ventral” vagal pathway is, according to PVT, newer (more recently evolved) and thus this is the part governing relaxed, prosocial affective states; the second “dorsal” vagal pathway is older and associated with “immobilized,” unhappy, or depressive states. PVT thus proposes a further distinction within the autonomic nervous system: first, sympathetic and parasympathetic, and then within the parasympathetic nervous system, the “dorsal” and “ventral” vagal pathways. (I surmise that, in the PVT hierarchy, the sympathetic nervous system, associated with extreme activation and “fight or flight” responses, would be the oldest and most primitive of all.)
The complex of theoretical claims associated with PVT is what has given rise to the now-ubiquitous pop-psychology speak about “the nervous system” and its various states of dys/regulation. (The theory has been widely popularized by influential psychologists like Bessel van der Kolk and Gabor Maté, who have incorporated many tenets of PVT into their theories of trauma and healing.) These claims also form the conceptual foundation for the Safe and Sound Protocol.
The Safe and Sound Protocol is a listening intervention designed to stimulate the “ventral” vagus and promote emotional regulation. It does so, according to UnyteHealth (formerly Integrated Listening Systems, which began offering the protocol in 2017, and for which Porges is Chief Scientific Adviser) by “recruiting” certain structures in the middle ear by playing voice or music recordings filtered to a specific sound frequency. (Vagus nerve fibers do indeed reach into the skin of the ear canal.) Marketing the intervention chiefly to therapists to assist with clients, UnyteHealth claims that the Safe and Sound Protocol is an “evidence-based listening therapy” that is “designed to shift the nervous system from defense to regulation.”
The problem is that none of this is true. Neither the claims about the Safe and Sound Protocol nor any of the claims PVT makes about the structure of the nervous system or its association with emotional states have any basis in fact. As Marta Smigielska writes in a comprehensive summary post, “all anatomical and evolutionary claims of PVT are false.” (I can’t say it any better than that!) A recent critique declaring PVT “untenable” has generated some controversy (related more to the impenetrable language of the critique itself and Porges’s response than to any lack of scientific consensus around the fundamental falsehood of PVT’s claims). The authors of the critique marshal an impressive quantity of research evidence that debunks or directly contradicts PVT’s claims about the evolution and organization of neural pathways and the role of the vagus nerve in the nervous system. There is no controversy about the factual correctness of the theory—PVT is dead in the water and its claims, about the vagus nerve and everything else, are nonsense.
Still, promoters of PVT have argued that its theoretical and biological incorrectness is irrelevant if it helps people practically. This argument could have some merit if PVT helps people practically. But does it? PVT is, as its name suggests, a theory. There are some therapeutic modalities that are associated with the theoretical worldview around PVT, but these either aren’t specific to the theory or are not really therapies. For an example of the former, breath work and mindfulness do work practically to relieve stress and promote mental health, but not because they stimulate the ventral vagus nerve. For an example of the latter, the couple I knew advocated for turning one’s head side to side as a way to stimulate the vagus nerve and regulate a distressed nervous system. This is apparently associated with the PVT worldview, but it can’t be considered a therapy.
There is, to my knowledge, only one actual intervention that is specific to PVT, in the sense of being designed specifically according to the PVT-derived understanding of how the nervous system is organized: the Safe and Sound Protocol. And the meager body of evidence that the Safe and Sound Protocol works in practice is not at all conclusive.
I conducted a (thorough but admittedly non-systematic) literature search in PubMed for studies evaluating the Safe and Sound Protocol or similar listening interventions. This search yielded only three papers evaluating the Safe and Sound Protocol that I considered eligible for closer review (I turned up two more, each case reports of a single patient, that I excluded). All three of the papers that I looked at tested the intervention on pediatric patients with autism: do these children show improvement in autism symptoms after receiving the Safe and Sound Protocol?
If the theory works even though its fundamental assumptions are wrong, we should see at least a moderate correlation between receiving the Safe and Sound Protocol and symptom improvement. None of the three papers I reviewed come close to establishing such a correlation. (Nor did they meet the higher threshold of providing evidence that the vagus nerve specifically is stimulated by the filtered music—a handful of questionnaire responses can’t tell researchers what the neurophysiological mechanism of action is.) UnyteHealth claims that the Safe and Sound Protocol is “evidence-based,” but the evidence it is based on is quite thin, and the intervention has not been approved by the US Food and Drug Administration.
In addition to being scientifically incorrect, then, there’s also no reliable evidence that PVT works practically to help people or relieve them of their symptoms or distress. This is not to say that there is no connection between the mind and the body. That much is undeniable, and the components of mind-body or somatic therapy that patients and clinicians find useful are, first, not specific to PVT and, second, completely agnostic to the underlying claims that PVT makes. (Again, deep breathing works, but not because it stimulates the vagus nerve.) PVT is influential not because of its efficacy, but because of the structure of vested interest and promotion supporting it, and because psychologists like Porges, van der Kolk, and Maté have woven compelling metaphorical narratives about trauma and healing around its scientific-sounding claims.
These metaphorical narratives are powerful, and can no doubt be intensely personally healing and meaningful. Metaphors, however, are not evidence in the scientific sense; while they can be useful to elucidate scientific concepts, there is a risk of confusing the assumptions embedded in the metaphor itself with empirical claims about reality. PVT promotes misunderstanding by popularizing pseudoscientific claims about the nervous system and how the nervous system relates to emotional experiences. It presents oversimplified and false claims as settled science in a specialized jargon difficult for clinicians and laypeople alike to critically evaluate.
Because these claims are so hard to evaluate in scientific terms, they are uniquely vulnerable to being incorporated into a seductive but ultimately misleading narrative about how the mind-body connection works in our complex social environments. And there’s no mistaking the ideological component stowed away in the evolutionary hierarchy of nervous system states at the core of PVT, with the more unpleasant or undesirable ones at the primitive bottom (or beginning) and the more desirable ones at the latest, most evolved top.
Curiously, by insisting that unhappy families are also all alike, at least at the level of the parasympathetic nervous system, PVT absents the mind from the mind-body connection: emotional states are reducible to involuntary electrical activity in the nerves. It is, of course, important to listen to the body, but the mind is also involved. What the body’s signals mean is still a matter of interpretation, which is to say, a matter of the mind. Recognizing what fear or anger feel like in the body is important somatic knowledge; thinking about why I am afraid or angry in a given situation—even if it’s “just” my partner forgetting to fold the laundry—is a task for the individual mind and its capacity for meaning-making.
As for the couple I knew, I’m no longer in touch with them. I hope that, over the many intervening years, they have found a more forgiving template for integrating embodied experience with emotional meaning.