Fundamental Challenges to Polyvagal Theory: A Plain-English Review

Grossman, P. (2023) — Biological Psychology

Polyvagal Theory has become an influential way of thinking about safety, threat, social connection and autonomic regulation. However, some of the scientific explanations underlying the theory have been challenged.

In this 2023 paper, researcher Paul Grossman examines several of the central biological and evolutionary claims made by Polyvagal Theory and argues that important parts of them are not supported by the available evidence.

This makes the paper particularly useful because it allows us to distinguish between the clinical usefulness of some Polyvagal ideas and the question of whether the theory's proposed biological mechanisms are scientifically established.

What does Grossman question?

Grossman focuses on five central premises of Polyvagal Theory.

These include claims concerning the evolution of the autonomic nervous system, differences between branches of the vagus nerve, the proposed relationship between these systems and different behavioural states, and the interpretation of measures such as respiratory sinus arrhythmia.

His argument is that findings from comparative anatomy, evolutionary biology and autonomic physiology present substantial difficulties for some of these claims.

In other words, his criticism isn't primarily about whether therapists or clients find Polyvagal concepts helpful. It concerns whether the biological explanation proposed for those concepts is accurate.

Why does this distinction matter?

A therapeutic framework can sometimes help us organise and understand experience without every part of its original scientific explanation ultimately proving correct.

For example, paying attention to whether someone feels sufficiently safe to connect, becomes mobilised in response to threat, or moves towards withdrawal or immobilisation can still be clinically meaningful observations.

But we should be careful about presenting a particular neurological explanation for those experiences as established fact when the science remains debated.

For me, that distinction is important.

Does this mean Polyvagal Theory has no value?

This paper does not settle the question of whether clinicians may find aspects of the Polyvagal framework useful.

Grossman's focus is on its scientific premises rather than testing Polyvagal-informed psychotherapy as a treatment.

In my own practice, I have found aspects of Polyvagal Theory useful alongside Somatic Experiencing, attachment theory and other understandings of nervous-system regulation.

The criticism in this paper doesn't require abandoning those observations. Instead, it encourages greater precision about what we know, what remains theoretical and what comes from clinical experience.

Holding theory and experience together

One of the things I value in therapeutic work is remaining curious rather than becoming too attached to a single explanation.

A client's immediate experience — changes in breathing, muscle tone, movement, sensation, emotion, connection or withdrawal — is something we can explore together.

We don't necessarily need to decide immediately which theoretical model explains it.

Polyvagal Theory can provide one useful map. Somatic Experiencing, attachment theory and other perspectives provide additional maps.

None needs to become the whole territory.

What I take from this paper

Grossman's critique is valuable precisely because Polyvagal Theory has become so influential.

If we use scientific language in therapy, it is important to remain open to the science changing.

For me, the most useful position is therefore neither to accept every aspect of Polyvagal Theory uncritically nor to discard the whole framework because some of its proposed mechanisms are disputed.

Instead, we can remain interested in what is clinically useful while being clear about the limits of the scientific evidence.

The next paper in this series looks at Polyvagal Theory again in light of more recent findings across neuroscience and related fields.

Reference

Grossman, P. (2023). Fundamental challenges and likely refutations of the five basic premises of the polyvagal theory. Biological Psychology, 180, 108589.

Read the original paper →