While the theory has been widely embraced in clinical spaces, some scientists have questioned whether the biological evidence behind it is strong enough.
In 2023, Paul Grossman published a paper outlining what he saw as major challenges to several key assumptions of Polyvagal Theory. More recently, he and 39 coauthors published a larger review arguing that many of the theory’s physiological and evolutionary claims may not hold up under closer scientific examination.
Interestingly, some of the researchers involved in the critique had previously been cited in support of the theory.
Questions About Measuring the Vagus Nerve
One of the biggest issues raised involves something called respiratory sinus arrhythmia (RSA).
RSA describes the natural change in heart rate that occurs while we breathe in and out. Researchers have often used RSA as an indirect way to estimate activity in the vagus nerve, which plays a key role in the autonomic nervous system.
Grossman and colleagues argue that RSA may not actually be a reliable measure of vagal activity. Instead, it can be influenced by many other factors, including age, cardiovascular health, and activity in other parts of the nervous system.
If RSA is not a clear indicator of vagal function, then many studies that relied on it to support Polyvagal Theory may need to be reinterpreted.
Questions About the Evolutionary Model
Another criticism focuses on the theory’s evolutionary explanation.
Polyvagal Theory suggests that the ventral vagal system is uniquely mammalian and evolved later to support social engagement and connection. Grossman and his colleagues argue that current biological evidence does not clearly support that evolutionary sequence.
They point out that similar neural pathways appear across many vertebrate species, which challenges the idea of a simple evolutionary “ladder” within the autonomic nervous system.
Concerns About “Dorsal Vagal Shutdown”
The researchers also question the commonly used concept of “dorsal vagal shutdown.” According to their analysis, the cardiac and neurological mechanisms often attributed to this state may not align with established neurophysiology.
These critiques challenge some of the most widely used interpretations of Polyvagal Theory in clinical settings.
Why This Conversation Matters
Beyond the academic debate, Grossman has expressed concern about how quickly Polyvagal Theory has been adopted in clinical and wellness spaces. In a 2024 LinkedIn post, he wrote that false explanations or exaggerated claims can create unrealistic expectations and potentially cause harm.
For mental health professionals, this raises an important question: How do we balance useful clinical ideas with strong scientific evidence?
What This Means for Trauma-Informed Practice
The growing debate does not mean that everything associated with Polyvagal Theory is incorrect. Many of the ideas that made the theory appealing like the connection between stress, safety, relationships, and the body are widely supported across multiple areas of research.
We know that:
• Chronic stress affects the nervous system
• Feelings of safety influence emotional regulation
• Trauma can show up in the body as well as the mind
Those insights remain central to trauma-informed care.
What this discussion does highlight is the importance of scientific humility. Sometimes theories that feel intuitively helpful still need stronger biological evidence.
For therapists and social workers, the goal is not to abandon helpful frameworks, but to stay curious and open to new research. As our understanding of the brain and body continues to grow, theories evolve and so does the way we support healing.
Moving Forward
The authors of the recent review have called for a careful re-evaluation of the biological claims behind Polyvagal Theory. Future research may refine the theory, revise it, or develop new models that better explain how the nervous system responds to stress and safety.
Regardless of where the science ultimately lands, one core truth remains: our bodies and minds are deeply connected.
Understanding that connection and helping people feel safer in their bodies and relationships continues to be a vital part of trauma-informed mental health care.