Dr. Stephen Porges, Ph.D formulated the groundbreaking polyvagal theory, which explains the relationship between the autonomic nervous system and social behavior and details how chronic stress can cause pain and other physical conditions.
What Is Polyvagal Theory?
Polyvagal theory helps us understand the complexity of the human nervous system. Before the formulation of polyvagal theory, the nervous system was thought of as a two-part antagonistic system. This antiquated binary model for understanding the stress response explained it as being either on or off, with a person being either stressed or not stressed. It was thought that when a threat, such as from a dangerous animal, activated the stress response, then the automatic nervous system would activate, mobilize, and respond, and then when the threat had been processed, the body would return to homeostasis or the rest-and-digest system.
Porges discovered that it is much more nuanced than that because humans actually have multiple states of stress, and therefore multiple states of nervous system activation. He provides a more complex scientific explanation of a three-part hierarchical model and explains how the vagus nerve is directly linked to a methodical system of communication and connection within the autonomic system.
The Nervous System and the Vagus Nerve
In order to understand polyvagal theory, one must have a basic knowledge of the sympathetic and parasympathetic nervous systems and the vagus nerve.
The vagus nerve serves the parasympathetic nervous system, which is the calming aspect of our nervous system mechanics, often dubbed the rest-and-digest system.
The parasympathetic component of the autonomic nervous system balances the sympathetic component, but in much more nuanced ways than was understood before 1994, when the polyvagal theory was first proposed by Porges.
Although numerous other nerves exist in the autonomic system, the vagus nerve is the longest cranial nerve and reaches most of the body’s organs.
Stephen Porges identified a hierarchy of responses built into our autonomic nervous system. This hierarchy has been a key part of the evolutionary development of humans.
Ventral Vagal Social Engagement
This is the state in which we are able to connect and relate to others and is characterized by openness, compassion, joy, mindfulness, and curiosity. Ventral vagal social engagement is the most recent addition to the evolutionary process and is tied to the parasympathetic nervous system. As a result, body processes such as digestion, immunity, circulation to the extremities, and our ability to relate to others and rest are enhanced, while defensive responses are decreased.
Sympathetic Nervous System Activation
The physical sympathetic nervous system evolved around 400 million years ago, around 200 million years before the ventral vagal social engagement system.
This is a state of mobilization, often referred to as fight-or-flight, in which the body is motivated to dispatch a threat. Arousal is increased as the sympathetic nervous system is activated. Blood pressure, heart rate, blood circulation, and adrenaline increase, while digestion, immunity, relational ability, and fuel storage all decrease. It is also linked to tension, anxiety, hyperactivity, and a more chaotic state.
Sympathetic activation cannot be maintained all the time; the increase in blood pressure and heart rate and the flood of adrenaline would eventually kill you. While the stress response is a survival mechanism that has kept humans alive, if it were activated all of the time, it would be detrimental to our health. Therefore, the body self-regulates, eventually adopting dorsal vagal shutdown to modulate a person’s sympathetic activation.2
Dorsal Vagal Shutdown
This is a much more primal part of human functioning, evolving about 500 million years ago. It is often understood as playing possum as it can often cause people to freeze, slow down, and feel immobilized, lethargic, hopeless, and trapped.3 In this state, a range of basic physical functions decrease, including heart rate, blood pressure, temperature regulation, and immune response. Less well-known is its impact on social functioning; eye contact, facial expressions, and intonation can be affected in addition to an adapted awareness of the human voice and social behavior.1
From a polyvagal perspective, the autonomic nervous system is the foundation upon which all lived experience exists. It explains how we engage with the world (in terms of activity and interactions with people) through connecting, disconnecting, and being attuned.
In contrast, some people experience a mismatch, and the nervous system identifies the environment as dangerous even when it is safe.
How This Affects Us
Polyvagal theory helps us understand the ways that stress is stored and processed in the body. Due to the adaptive responses in activated states, the way that people perceive the world can actually change.3 This alteration can cause sensory stimulation that shouldn’t feel painful to be interpreted as painful by the brain, and understanding this has been seismic in supporting individuals with chronic pain that is related to trauma or stress. On a neurological level, the brain becomes more sensitive to threats and interprets non-threatening input as dangerous. This can cause neutral facial expressions to appear aggressive and threatening. The brain may also become hypersensitive to low-frequency sounds that imitate the growl of a predator.2 Constantly perceiving the world to be stressful, dangerous, painful, and threatening can be emotionally exhausting and physically draining. It can affect work, relationships, hobbies, and studies. Perceiving a stimulus as threatening can greatly impact relationships if a person processes a benign stimulus as threatening and dangerous when their friend, partner, or family member is actually trying to comfort or support them. Supporting your own well-being or the well-being of a loved one means responding to the state that they are in and understanding their needs in each state of activation. This information is also helpful for counselors and other mental health professionals.
Making use of body-awareness techniques that are often used in both cognitive behavioral therapy (CBT) and dialectical behavioral therapy (DBT) can be useful in helping clients shift from dorsal vagal shutdown, where they experience dissociative, shutdown responses, to a more embodied state.
Shifting from dorsal vagal shutdown entails moving toward the fight-or-flight sensations, so adopting the thought-restructuring techniques that are also part of CBT and DBT can help clients more effectively evaluate their safety and become less hypersensitive to threats.
Adding a polyvagal perspective to clinical practice directly acknowledges the autonomic nervous system’s role in therapy. This can help clients re-pattern their nervous systems, build capacities for better regulation, and create autonomic pathways of connection and safety. Porges states that even in adverse conditions, such as the noisy or stressful environment of an emergency room after a disaster, mind-body techniques including deep breathing, posture, and vocalization can help an individual shift into a state of mental and physical calmness.3
The polyvagal theory offers a wealth of opportunities for better supporting individuals who have long been at the behest of a dysfunctional autonomic nervous system.
 Porges S. W. (2009). The polyvagal theory: new insights into adaptive reactions of the autonomic nervous system. Cleveland Clinic journal of medicine, 76 Suppl 2(Suppl 2), S86–S90. https://doi.org/10.3949/ccjm.76.s2.17
 Porges S. W & Dana D. (2018). Clinical Applications of the Polyvagal Theory: The Emergence of Polyvagal-Informed Therapies. New York: WW Norton.
 Porges, S. W. (2011). The polyvagal theory: Neurophysiological foundations of emotions, attachment, communication, and self-regulation. W.W. Norton.
 Dana, D. (2018). The polyvagal theory in therapy: Engaging the rhythm of regulation. W W Norton & Co.