As an EMDR therapist working with adults, children, and adolescents in Southeast Sydney and online, I frequently help clients understand how trauma affects the nervous system. Many people come to therapy wondering why they feel anxious, overwhelmed, disconnected, emotionally reactive, or stuck despite their best efforts to cope. 

Two concepts that have become increasingly influential in trauma-informed therapy are Polyvagal Theory and the Window of Tolerance. Together, they help explain how our nervous system responds to stress, danger, relationships, and traumatic experiences, offering a compassionate framework for understanding emotional and physiological reactions. 

Rather than asking, “What is wrong with me?”, these models encourage us to ask, “What has my nervous system learned to do in order to keep me safe?” 

One of my mentors describes the autonomic nervous system as “150-million-year-old software”: an ancient survival system designed to detect safety, danger, and threat. From this perspective, responses such as fight, flight, and freeze are not signs of weakness or failure, but evolutionary responses that have developed to help us survive. 

What is Polyvagal Theory?

Polyvagal Theory was developed by neuroscientist Dr Stephen Porges and provides a neurophysiological framework for understanding how the autonomic nervous system responds to safety, danger, and life threat (Porges, 2007; Porges, 2025). The theory highlights the central role of the vagus nerve in regulating emotional states, social connection, physiological functioning, and behavioural responses. 

According to Polyvagal Theory, the nervous system is continuously scanning the environment for cues of safety or threat through a largely unconscious process known as neuroception (Porges, 2007; Porges, 2025). Depending on what the nervous system detects, individuals shift between different autonomic states that influence how they think, feel, and behave. 

The Three Primary Nervous System States

1. Ventral Vagal State: Safety, Connection and Regulation

When the nervous system perceives safety, the ventral vagal system becomes dominant. Individuals typically feel calm, grounded, emotionally regulated, and socially connected. In this state, people are generally able to think clearly, communicate effectively, learn new information, and engage positively in relationships (Porges, 2007; Porges, 2011). 

Children in a ventral vagal state are often more able to learn, play, explore, and cooperate. Adults are more likely to feel present, emotionally balanced, and capable of navigating life’s challenges. 

2. Sympathetic State: Fight or Flight

When the nervous system detects danger, the sympathetic branch of the autonomic nervous system mobilises the body for action. This is commonly referred to as the fight-or-flight response (Porges, 2007). 

Symptoms associated with sympathetic activation may include: 

• Anxiety
  
  

• Panic
  
  

• Hypervigilance
  
  

• Irritability
  
  

• Racing thoughts
  
  

• Increased heart rate
  
  

• Muscle tension
  
  

• Difficulty relaxing
  
  

These responses are adaptive when facing genuine danger. However, trauma survivors may experience sympathetic activation even in situations that are objectively safe because their nervous system has become sensitised to potential threat (Van der Kolk, 1994; Porges, 2007). 

3. Dorsal Vagal State: Shutdown and Disconnection

When a threat is perceived as overwhelming or inescapable, the nervous system may shift into a dorsal vagal state. This immobilisation response can result in emotional and physical shutdown (Porges, 2007). 

Individuals may experience: 

• Emotional numbness
  
  

• Dissociation
  
  

• Fatigue
  
  

• Withdrawal
  
  

• Hopelessness
  
  

• Reduced motivation
  
  

• Feelings of disconnection
  
  

Research suggests that chronic trauma, particularly relational trauma occurring during childhood, can contribute to patterns of dissociation and difficulties with emotional regulation that persist into adulthood (Schore, 2001). 

Understanding the Window of Tolerance

The concept of the Window of Tolerance was originally developed by psychiatrist Dr Dan Siegel and has become a cornerstone of contemporary trauma therapy (Siegel, 1999; Siegel, 2012). 

The Window of Tolerance refers to the zone of emotional and physiological arousal in which an individual can function effectively, maintain emotional regulation, process information, and respond flexibly to stress. 

When people remain within their window of tolerance, they can experience a range of emotions without becoming overwhelmed. They may feel stressed, challenged, upset, or excited while still maintaining their capacity to think, reflect, and make considered decisions. 

Hyperarousal: Above the Window

When activation rises beyond the upper boundary of the window, individuals may enter a state of hyperarousal. 

Common experiences include: 

• Anxiety
  
  

• Panic
  
  

• Anger
  
  

• Hypervigilance
  
  

• Emotional reactivity
  
  

• Difficulty concentrating
  
  

• Sleep disturbance
  
  

Hyperarousal closely reflects sympathetic nervous system activation and the fight-or-flight response described in Polyvagal Theory (Corrigan, Fisher and Nutt, 2011). 

Hypoarousal: Below the Window

When activation drops below the lower boundary of the window, individuals may enter a state of hypoarousal. 

Common experiences include: 

• Emotional shutdown
  
  

• Dissociation
  
  

• Numbness
  
  

• Withdrawal
  
  

• Fatigue
  
  

• Low motivation
  
  

• Feelings of disconnection
  
  

Hypoarousal closely resembles the dorsal vagal response described by Polyvagal Theory and is often observed in individuals with histories of complex trauma (Corrigan, Fisher and Nutt, 2011; Schore, 2001). 

How Trauma Narrows the Window of Tolerance

Traumatic experiences can significantly influence how the nervous system responds to future stressors. The brain becomes increasingly focused on detecting danger, often resulting in a narrowing of the Window of Tolerance (Siegel, 2012). 

As a result, people may move rapidly into states of hyperarousal or hypoarousal in response to situations that others may perceive as relatively manageable. 

For example: 

• A child exposed to chronic family conflict may become highly reactive to raised voices.
  
  

• A teenager who has experienced bullying may become extremely anxious in social situations.
  
  

• An adult who has experienced trauma may find everyday stress triggers intense emotional reactions.
  
  

From a trauma-informed perspective, these responses are not signs of weakness. Rather, they reflect adaptive survival responses developed by the nervous system to enhance protection in the face of perceived threat (Van der Kolk, 1994; Schore, 2001). 

The Importance of Co-Regulation

One of the most significant contributions of Polyvagal Theory is its emphasis on the role of relationships in regulating the nervous system. Humans are biologically wired for connection, and experiences of safety are often developed and maintained through relationships (Porges, 2007; Porges, 2025). 

Children rely heavily on caregivers to help regulate their emotional and physiological states. Similarly, adults often benefit from supportive relationships that foster feelings of safety, trust, and connection. 

This concept is known as co-regulation and is increasingly recognised as a key factor in trauma recovery and emotional wellbeing. 

See our children and adolescent page for counselling services available for young people and the importance of working systemically.

Polyvagal Theory, the Window of Tolerance and EMDR Therapy

EMDR (Eye Movement Desensitisation and Reprocessing) is an evidence-based psychotherapy widely recognised as an effective treatment for trauma and post-traumatic stress disorder (Shapiro, 2014; Miller, 2024). 

Many clients beginning EMDR therapy spend considerable time outside their Window of Tolerance. Some become easily overwhelmed by anxiety and intrusive memories, while others experience emotional numbness, avoidance, or dissociation. 

A key part of EMDR therapy involves helping clients develop the capacity to remain sufficiently regulated while processing distressing memories. As traumatic experiences are reprocessed, many individuals report: 

• Reduced emotional reactivity
  
  

• Increased emotional regulation
  
  

• Greater resilience to stress
  
  

• Improved self-awareness
  
  

• Increased feelings of safety and connection
  
  

• Enhanced capacity to remain present
  
  

Although EMDR and Polyvagal Theory are distinct frameworks, both recognise the importance of nervous system regulation in trauma recovery (Shapiro, 2018; Porges, 2025). 

Supporting Nervous System Regulation

While every individual is different, several evidence-informed approaches may support nervous system regulation and help widen the Window of Tolerance: 

• Strong and supportive relationships
  
  

• Trauma-focused therapy
  
  

• EMDR therapy
  
  

• Mindfulness practices
  
  

• Breathwork and grounding exercises
  
  

• Regular physical activity
  
  

• Healthy sleep routines
  
  

• Consistent daily structure
  
  

• Sensory regulation strategies for children and adolescents
  
  

Over time, these approaches may help individuals develop greater flexibility within their nervous system, allowing them to navigate stress more effectively. 

Current Scientific Perspectives

Polyvagal Theory has had a significant influence on trauma-informed practice, psychotherapy, education, and healthcare. However, some aspects of the theory continue to be debated within the scientific literature. Critics have questioned certain evolutionary and neurophysiological assumptions associated with the model (Grossman et al., 2025). 

Despite these debates, many clinicians and researchers continue to regard autonomic regulation, social engagement, and nervous system states as useful concepts for understanding trauma and emotional wellbeing, while research in these areas continues to evolve (Porges, 2025). 

Conclusion

Polyvagal Theory and the Window of Tolerance provide valuable frameworks for understanding how the nervous system responds to stress, trauma, and relationships. These concepts help explain why people may become anxious, reactive, disconnected, or overwhelmed, particularly following adverse life experiences. 

For adults, adolescents, and children, developing awareness of nervous system states can be an important step towards healing. Through evidence-based approaches such as EMDR therapy, individuals can learn to regulate emotional responses, process traumatic memories, expand their Window of Tolerance, and build a greater sense of safety, resilience, and connection in everyday life. 

References

Corrigan, F.M., Fisher, J.J. and Nutt, D.J. (2011) ‘Autonomic dysregulation and the Window of Tolerance model of the effects of complex emotional trauma’, Journal of Psychopharmacology, 25(1), pp. 17–25. 

Grossman, P., Ackland, G.L., Allen, A.M., Berntson, G.G., Booth, L.C., Burghardt, G.M., Buron, J., Dinets, V., Doody, J.S. and others (2025) ‘Why the Polyvagal Theory is untenable: An international expert evaluation of the Polyvagal Theory and commentary upon Porges (2025)’, Clinical Neuropsychiatry, 22(3), pp. 192–222. 

Miller, P.W. (2024) ‘The evolution and future of eye movement desensitisation and reprocessing therapy’, BJPsych Advances, 30(4), pp. 239–241. 

Porges, S.W. (2007) ‘The polyvagal perspective’, Biological Psychology, 74(2), pp. 116–143. 

Porges, S.W. (2011) The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication and Self-Regulation. New York: W.W. Norton. 

Porges, S.W. (2025) ‘Polyvagal theory: a journey from physiological observation to neural innervation and clinical insight’, Frontiers in Behavioral Neuroscience, 19. Available at: https://doi.org/10.3389/fnbeh.2025.1659083. 

Schore, A.N. (2001) ‘The effects of early relational trauma on right brain development, affect regulation, and infant mental health’, Infant Mental Health Journal, 22(1–2), pp. 201–269. 

Shapiro, F. (2014) ‘The role of Eye Movement Desensitization and Reprocessing (EMDR) therapy in medicine: addressing the psychological and physical symptoms stemming from adverse life experiences’, The Permanente Journal, 18(1), pp. 71–77. 

Shapiro, F. (2018) Eye Movement Desensitization and Reprocessing (EMDR) Therapy: Basic Principles, Protocols and Procedures. 3rd edn. New York: Guilford Press. 

Siegel, D.J. (1999) The Developing Mind: Toward a Neurobiology of Interpersonal Experience. New York: Guilford Press. 

Siegel, D.J. (2012) The Developing Mind: How Relationships and the Brain Interact to Shape Who We Are. 2nd edn. New York: Guilford Press. 

Van der Kolk, B.A. (1994) ‘The body keeps the score: memory and the evolving psychobiology of posttraumatic stress’, Harvard Review of Psychiatry, 1(5), pp. 253–265. 

Van der Kolk, B.A. (2014) The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma. New York: Viking.

As an experienced social worker working across community mental health, counselling services, palliative care, emergency departments, and now victim services, I have supported individuals through many forms of grief — from expected loss to sudden, traumatic bereavement. 

When I first began my training in EMDR therapy (Eye Movement Desensitisation and Reprocessing), I was initially surprised — and somewhat hesitant — to learn that EMDR could be used as a treatment for grief. At the time, I associated EMDR primarily with trauma. However, my clinical perspective has evolved significantly. 

Can EMDR Help with Grief?

Emerging research suggests that EMDR is an effective intervention for individuals experiencing complicated or prolonged grief, where the mourning process becomes persistent and distressing. Prolonged Grief Disorder can significantly impact emotional wellbeing, functioning, and quality of life (Spicer, 2024). 

EMDR is grounded in the Adaptive Information Processing (AIP) model, which proposes that distressing experiences — including aspects of bereavement — can become “stuck” in memory networks. This can prevent individuals from integrating the loss and accessing more adaptive or meaningful memories of the deceased (Solomon & Rando, 2012). 

Through structured processing, EMDR helps individuals: 

• Reduce the emotional intensity of distressing memories
  
  

• Reprocess traumatic aspects of the loss
  
  

• Integrate the experience more adaptively
  
  

• Reconnect with more positive or nostalgic memories
  
  

When Is EMDR Useful for Grief?

In my clinical work, EMDR has been particularly helpful in cases of traumatic bereavement or unresolved grief, including: 

• Sudden or premature death
  
  

• Death by suicide or homicide
  
  

• Shock-related losses
  
  

• Persistent, overwhelming sadness
  
  

• Situations where distressing memories overshadow meaningful reflections of the loved one
  
  

In these presentations, grief is often intertwined with trauma. EMDR helps process these distressing elements so that the grieving process can continue in a more natural and integrated way. 

What Does the Research Say?

A randomised controlled trial found that EMDR significantly reduced grief symptoms, trauma symptoms, and emotional distress, with outcomes comparable to cognitive behavioural therapy (CBT) (Meysner, Cotter & Lee, n.d.). 

Similarly, recent research highlights EMDR as a promising therapy for prolonged grief, supporting individuals to process past memories, current triggers, and future fears associated with the loss (Spicer, 2024). 

A Shift in Clinical Practice

My initial hesitation has shifted to a deep appreciation of EMDR as a valuable approach in grief work. While EMDR does not “remove” grief — nor should it — it can reduce the intensity of traumatic distress that may be blocking the natural mourning process. 

For many clients, this creates space for grief to evolve into something more bearable, meaningful, and integrated. 

Find out more about EMDR on this website.

References 

Meysner, L., Cotter, P. & Lee, C.W. (n.d.) Evaluating the efficacy of EMDR with grieving individuals: A randomized control trial. Available at: link_titlehttps://spj.science.org/doi/pdf/10.1891/1933-3196.10.1.2turn1search3 

Solomon, R.M. & Rando, T. (2012) Treatment of grief and mourning through EMDR: Conceptual considerations and clinical guidelines. European Review of Applied Psychology, 63(4), pp.231–239. Available at: link_titlehttps://www.emdria.org/resource/treatment-of-grief-and-mourning-through-emdr-conceptual-considerations-and-clinical-guidelines-european-review-of-applied-psychology/turn1search12 

Spicer, L. (2024) Eye Movement Desensitisation and Reprocessing (EMDR) therapy for prolonged grief: theory, research, and practice. Frontiers in Psychiatry. Available at: link_titlehttps://pmc.ncbi.nlm.nih.gov/articles/PMC11056564/turn1search1 

See our EMDR page for EMDR specialised psychotherapy services