“If you want to improve the world, start by making people feel safer.”
The polyvagal theory offers key insights into the ways that nervous system dysregulation as a result of trauma impacts physical and emotional well-being.
The Autonomic Nervous System States
The autonomic nervous system (ANS) is responsible for scanning an environment for threats and dangers. If a threat is detected, a well-regulated autonomic nervous system will respond accordingly. This is often referred to as the stress response and is understood by many as fight-or-flight. There are three general states that the autonomic nervous system will be in: same, mobilized, or immobilized. In polyvagal theory, the safe state is called ventral vagal social engagement and is the state in which we can connect and relate to others or the environment with curiosity, mindfulness, and openness. The mobilized state is referred to as sympathetic nervous system activation. In this state, blood pressure, heart rate, blood circulation, and adrenaline levels all increase, while digestion, immunity, and relational ability all decrease. These effects help you in situations where you might need to think or act quickly. Eyesight, reflexes, endurance, and strength are all heightened for your fight-or-flight reaction. The immobilized state is called dorsal vagal shutdown and initiates the freeze response.1 When the ANS detects a threat that you cannot fight or run away from, heart rate and blood pressure are released, while pain-numbing endorphins are released. A healthy, well-regulated autonomic nervous system will move fluidly from one state to another; however, a dysregulated ANS can fail to recognize safety and danger and can shift from one state to another. Trauma and chronic stress, especially in early childhood, can be one cause of ANS dysregulation.5
The ANS can become hypersensitive, perceiving threats or dangers that don’t actually exist. Living in the mobilized or immobilized states, as a result, can be debilitating, resulting in chronic pain, digestion issues,5 and trouble connecting and socializing.1 This can result in maladaptive coping mechanisms, such as drug use, sex, gambling, and unhealthy eating habits.
Trauma and the Autonomic Nervous System
The causes of trauma are wide-ranging and complex. Trauma is now well-understood as an experience as opposed to an event, because an event that is traumatic to one person may not be for another. Some common causes of trauma in early life include childhood neglect, abuse, parental drug use or incarceration, and adverse childhood experiences (ACE’s) such as living in a dangerous or impoverished neighborhood. These can all cause relational or developmental trauma, and research shows that experiencing up to three adverse childhood experiences increases the risk of asthma, heart disease, depression, anxiety, and obesity. It is thought that this is partially a result of the way that this compounded stress or trauma affects the central nervous system, which is responsible for basic functions like digestion, breathing, and blood circulation.5 When trauma disrupts ANS functioning, the vagus nerve, which sends messages from the brain to the digestive system and heart, can encounter difficulties with communicating.1 Emerging research shows that physical and emotional symptoms can emerge from a chronically dysregulated ANS because it is constantly searching for threats. A number of common illnesses, such as digestive disorders, autoimmune diseases, and chronic fatigue, as well as psychological problems such as depression, anxiety, PTSD, and substance use disorders, are all linked to trauma or chronic stress. In addition to the effect on health, early childhood experiences of connection can directly impact relationships in the future. Experiencing violence, neglect, or inconsistent and inattentive parenting can cause the ANS to become over-protective in adulthood. Due to chronic feelings of danger or uncertainty around primary caregivers as a child, it is common for adults to reject intimacy and connection because it is deemed dangerous, even though love and connection are what we really desire. The need for connection is replaced with the need for protection.
Although adverse childhood experiences have particularly profound effects on development and health, traumatic experiences at any time can disrupt the autonomic nervous system. Accidents, assaults, natural disasters, traumatic childbirth, and chronic stress can all cause dysregulation. There is emerging evidence that even genetics can influence nervous system regulation, as epigenetics research reveals trauma can be passed on genetically.
For people with a history of trauma, the ANS reacts not only to the perceived safety or danger in their immediate environment but also to the internal interaction between the immediate environment and a sense of fear or stress that is triggered from past life events.
Importance for Recovery
The polyvagal theory offers a better understanding of how the ANS works and accounts for the complexity of shifting between states. There is also a range of insights that can be adopted to better support individuals in treatment for both physical and mental disorders or symptoms.
The polyvagal theory has demonstrated the dual function of the parasympathetic nervous system. Previously understood as related only to rest-and-digest, its role in the symptoms of PTSD is now better understood. Steven Porges’ work demonstrates the evolutionary survival mechanism that the parasympathetic nervous system leads us to adopt. This is what causes immobilization or fainting when faced with a life-threatening situation. In addition, polyvagal theory highlights the importance of engaging the social nervous system to consciously inhibit the defensive system, which is key in trauma recovery. Learning to activate the social nervous system can be done by developing mindful awareness of somatic sensations such as your heart rate or breath. There is increasing evidence that yoga, involving both movement and regulated breath, is associated with improved sleep, quality of life, and lower rates of depression and subjective neurocognitive complaints. Regular yoga is also associated with a change in cortisol output and life satisfaction in veterans with PTSD.8
The polyvagal theory reaffirms the need for a sense of safety for clients in therapy. It offers counselors a better understanding of defense mechanism hierarchy. Recognizing shifts from fight-or-flight to immobilization or freeze mode when clients are feeling trapped, in addition to the shift from freeze into fight-or-flight, means that responses and strategies can be adapted accordingly. As individuals who make up wider communities, we can use polyvagal theory to question how we can better support each other through periods of stress and in response to trauma.
 Kolacz, J., & Porges, S. W. (2018). Chronic Diffuse Pain and Functional Gastrointestinal Disorders After Traumatic Stress: Pathophysiology Through a Polyvagal Perspective. Frontiers in medicine, 5, 145. https://doi.org/10.3389/fmed.2018.00145
 Herzog, J. I., & Schmahl, C. (2018). Adverse Childhood Experiences and the Consequences on Neurobiological, Psychosocial, and Somatic Conditions Across the Lifespan. Frontiers in psychiatry, 9, 420. https://doi.org/10.3389/fpsyt.2018.00420
 Daskalakis, N. P., Rijal, C. M., King, C., Huckins, L. M., & Ressler, K. J. (2018). Recent Genetics and Epigenetics Approaches to PTSD. Current psychiatry reports, 20(5), 30.
 Zaccari, B., Callahan, M. L., Storzbach, D., McFarlane, N., Hudson, R., & Loftis, J. M. (2020). Yoga for veterans with PTSD: Cognitive functioning, mental health, and salivary cortisol. Psychological trauma : theory, research, practice and policy, 12(8), 913–917. https://doi.org/10.1037/tra0000909