Talking about Polyvagal Theory: what practitioners in trauma-informed fields should know

Polyvagal Theory is one of the most widely recognised frameworks referenced in trauma-informed practice. Across mental health, healthcare, education and social services, the theory has helped many practitioners understand how the nervous system responds to safety, threat and overwhelming experiences.

For many clinicians and survivors, the language of Polyvagal Theory has provided an accessible way to explain why trauma responses are often physical, automatic and outside conscious control.

At the same time, aspects of the biological explanations proposed by Polyvagal Theory have been the subject of scientific debate within autonomic neuroscience and psychophysiology for many years. More recently, a large group of researchers led by Paul Grossman published a detailed critique examining whether some of the physiological mechanisms proposed by the theory are supported by current scientific evidence.

For practitioners working in trauma-informed fields, it is helpful to understand both the contributions of Polyvagal Theory and the nature of this ongoing scientific discussion.

Polyvagal Theory, originally developed by Stephen Porges, describes how the autonomic nervous system responds to perceived safety and danger.

The theory proposes that the nervous system operates through a hierarchy of responses that support survival.

1. Ventral vagal state – safety and social engagement

When individuals feel safe enough, the nervous system supports connection, communication and regulation. In this state people are able to think clearly, interact with others and remain present in their bodies.

2. Sympathetic state – mobilisation (fight or flight)

When the nervous system detects danger, the sympathetic nervous system prepares the body for action. This may involve increased heart rate, muscle tension, heightened alertness and readiness to defend or escape.

3. Dorsal vagal state – shutdown or collapse

When threat feels overwhelming or inescapable, the theory proposes that a dorsal vagal pathway may activate. This state is often described as involving shutdown, immobilisation, dissociation or collapse.

Polyvagal Theory links these responses to different branches of the autonomic nervous system. It also introduced the concept of “neuroception”, referring to the nervous system’s automatic detection of cues of safety or danger.

Polyvagal Theory has been widely adopted across trauma-informed fields for several reasons.

First, it provided a framework that helped connect psychological experience with physiological processes. It offered a way of explaining how trauma can affect the body and nervous system, not only thoughts and emotions.

Second, the theory helped reframe behaviours often seen in trauma survivors. Responses such as anxiety, withdrawal, dissociation or emotional numbing could be understood as adaptive survival responses rather than personal weakness or pathology.

Third, Polyvagal Theory reinforced principles that are central to trauma-informed practice, including:

• the importance of safety
• the role of relationships and co-regulation
• the impact of perceived threat on behaviour and functioning
• the connection between physiological regulation and emotional wellbeing

For many practitioners working with people impacted by complex trauma, the theory offered language that resonated with both clinical experience and survivors’ lived and living experience.

Although Polyvagal Theory has been widely used in clinical and educational settings, some of its biological claims are being increasingly questioned. In particular, scientists have examined whether the specific physiological mechanisms proposed by the theory accurately reflect current understanding of autonomic nervous system function.

A recent critique led by Grossman and colleagues, involving dozens of researchers in physiology and neuroscience, summarised many of these concerns. The authors argue that some aspects of the physiological model proposed by Polyvagal Theory are not supported by current evidence.

The critique focuses on a number of key areas:

1. Interpretation of heart rate variability

Polyvagal Theory often uses respiratory sinus arrhythmia (RSA), a component of heart rate variability, as an indicator of vagal regulation.

However, many researchers argue that RSA reflects multiple physiological processes and cannot be interpreted as a direct measure of vagal output alone. Heart rate variability appears to reflect broader regulatory processes involving several interacting neural and physiological systems.

2. The “dorsal vagal shutdown” model

Another area of debate concerns the idea that a dorsal vagal pathway directly produces shutdown or collapse responses.

Critics argue that most cardiac vagal regulation originates from a different brainstem structure, the nucleus ambiguus, rather than the dorsal motor nucleus often referenced in Polyvagal Theory.

In contemporary neuroscience, states such as freeze, collapse and dissociation are understood to involve multiple interacting systems, including:

• brain threat detection circuits such as the amygdala
• midbrain defence systems such as the periaqueductal gray stress hormone systems
• complex interactions between sympathetic and parasympathetic regulation

This suggests that shutdown states may emerge from distributed neural systems rather than a single vagal pathway.

3. Evolutionary claims

Polyvagal Theory also proposes an evolutionary hierarchy in which mammalian nervous systems developed specialised vagal pathways that support social engagement.

Some neuroscientists argue that aspects of this evolutionary account are overstated, noting that similar cardiorespiratory mechanisms appear across a wide range of vertebrate species.

It is important to recognise that these debates are not new. Concerns about aspects of Polyvagal Theory have been raised in scientific literature for approximately 15–20 years, particularly within fields such as autonomic physiology, psychophysiology and comparative neurobiology.

What is more recent is the publication of larger collaborative critiques that bring together multiple experts to summarise these concerns more clearly. This reflects a broader process of scientific refinement, rather than a sudden overturning of existing knowledge.

Current neuroscience generally explains stress regulation using network-based models of brain–body interaction.

One widely used framework is the Central Autonomic Network (CAN). This network includes multiple interacting brain regions such as:

• the prefrontal cortex
• the amygdala
• the insula
• the hypothalamus
• brainstem autonomic centres

Together these systems regulate physiological processes including heart rate, breathing, emotional responses, stress hormone activity, body awareness and interoception. In this view, regulation is dynamic and context-dependent, emerging from the interaction of multiple neural and physiological systems.

Alongside these developments, several other scientific frameworks have been increasingly used to understand regulation and trauma responses.

Neurovisceral Integration Theory

Linking heart rate variability to regulatory connections between the prefrontal cortex and autonomic systems.

Predictive processing models

Understanding threat responses as arising from the brain’s predictions about safety and danger based on past experience and sensory input.

Psychoneuroimmunology

Examining interactions between stress physiology, immune activity and inflammation.

Attachment and developmental neuroscience

Highlighting how relational safety and caregiving relationships shape the development of regulation across the lifespan.

These models tend to emphasise complex, interacting regulatory systems rather than discrete physiological states.

The current scientific debate does not undermine trauma-informed practice.

The discussion concerns the biological mechanisms proposed by Polyvagal Theory, not the core insight that trauma profoundly affects physiological regulation. A large body of research continues to support key principles widely used in trauma-informed approaches, including:

• trauma affects both body and mind
• safety and predictability support regulation
• relationships and co-regulation are central to healing
• physiological regulation is closely linked to emotional and cognitive functioning
• trauma responses are adaptive survival strategies

These principles remain strongly supported by research across neuroscience, developmental psychology and trauma studies.

As trauma science evolves, an important distinction is increasingly recognised between clinical models and precise biological mechanisms.

Simplified models can be valuable in practice because they:

• help explain complex processes in accessible ways
• support psychoeducation with clients
• provide shared language for practitioners

At the same time, the scientific explanations underlying these models may continue to evolve as new research emerges.

For trauma-informed practitioners, this means remaining open to ongoing scientific refinement while continuing to prioritise safety, compassion and relational care.

Polyvagal Theory played an important role in shifting attention toward the body and nervous system within trauma work. It helped many practitioners and survivors recognise that trauma responses are physiological survival strategies.

The current scientific discussion reflects the natural development of trauma science as research becomes more sophisticated. Increasingly, models of regulation emphasise:

• brain–body integration
• network-based regulation
• multisystem stress responses
• the role of relational safety in regulation

This evolution is a sign of a field that continues to deepen its understanding of how trauma affects human functioning.