What is the vagus nerve and how does it affect my mood?

Interview with Dr John Moran, Clinical Psychologist

Polyvagal-informed therapy is becoming an increasingly popular way of understanding stress, trauma and emotional overwhelm through the lens of the nervous system... Kathy Martin, a psychologist at the Paris Psychology Centre trained in polyvagal therapy, explains what the approach means in practice and how it can help.

What is polyvagal-informed therapy, and what does “polyvagal” actually mean?

Polyvagal theory emerged in the 1990s from the work of Dr Stephen Porges, who studied the fine-grained functioning of the autonomic nervous system. It was later adapted for therapeutic use by clinician and writer Deb Dana. The term polyvagal refers to the two branches of the vagus nerve involved in these state changes. The ventral vagal branch is associated with feeling grounded, connected and safe enough to engage. The dorsal vagal branch is associated with shutdown or collapse when the system feels overwhelmed.

In simple terms, this approach looks at how the nervous system responds to safety, stress and threat. The autonomic nervous system helps regulate processes such as heart rate, breathing, digestion and stress hormones. These bodily shifts, often outside our awareness, shape how able we are to feel calm, connected and present.

When the nervous system feels safe enough, we tend to be in what is often called a safe and social state: open, engaged, curious and able to relate to other people. This overlaps with the idea of the window of tolerance, the zone in which we can think clearly, feel our emotions without being overwhelmed and respond flexibly.

Under stress, the nervous system can move out of this zone in two main ways. Some people become mobilised: anxious, tense, angry, restless, driven to argue, act or escape. Others become immobilised or collapsed: shut down, numb, flat, disconnected or mentally checked out.

How does a polyvagal perspective change the way we understand anxiety, stress and burnout?

It gives us a more compassionate and practical way of understanding distress. Instead of seeing anxiety, overwhelm or shutdown simply as weakness or dysfunction, we can understand them as nervous system responses to stress or perceived threat.

This perspective can help people notice their patterns earlier and learn ways of regulating themselves before they become too overwhelmed. It also highlights the importance of co-regulation: the calming effect of safe connection with another person, and sometimes with animals too.

Why do some people become hyper-alert under stress, while others shut down or go numb?

People differ in how their nervous systems respond. These patterns are shaped by temperament, biology and life experience. Early relationships matter, especially whether caregivers were consistently responsive and emotionally attuned. Trauma, neglect and chronic stress can also narrow a person’s window of tolerance, making it easier to tip into hyperarousal or shutdown.

Some neurodivergent people may also experience a narrower window of tolerance, which can mean they become overstimulated or depleted more easily.

How can understanding the nervous system help people feel less ashamed or self-critical about their reactions?

It can be a great relief to realise that many reactions are not chosen consciously. They are bodily survival responses. Understanding this often reduces shame and makes self-compassion more possible.

That does not mean we are powerless. Rather, it creates a better starting point for change. If we understand what our nervous system is doing, we are often better able to respond with care, support and skill instead of blame.

What are some signs that someone may be living in a prolonged state of survival mode?

Survival mode can look different from person to person. In a more mobilised state, it may show up as anxiety, irritability, overthinking, panic, overwhelm, anger, compulsive behaviour, impulsivity, rigidity, difficulty relaxing or a constant feeling of being on edge.

In a more immobilised state, it may show up as exhaustion, emotional flatness, numbness, disconnection, memory problems, brain fog, withdrawal, going through the motions on autopilot or feeling stuck and unable to act. Some people move between the two.

What does a polyvagal-informed therapy session actually look like in practice?

A polyvagal-informed therapist usually pays close attention not just to what a person says, but to signs of nervous system state: changes in energy, voice, facial expression, breathing, posture and pace.

In couples work, for example, this can be especially useful. It can help partners recognise their own patterns of activation and withdrawal, understand how they affect each other and learn how to restore a sense of safety when conflict arises. This may involve naming state changes, slowing things down, improving communication and practising ways of co-regulating rather than escalating.

Is polyvagal-informed therapy mainly for trauma, or can it also help with everyday stress, relationship difficulties and emotional overwhelm?

It can be very helpful for trauma, especially when integrated with other approaches such as EMDR. But it is not only for trauma. It can also be valuable for everyday stress, burnout, emotional overwhelm, relationship difficulties and parenting challenges.

"Forgiveness is not something we do for the person who hurt us, but to reclaim our own peace."

Many people find it useful simply because it gives them a clearer map of what is happening in their body and mind under pressure.

Are there simple things people can do in daily life to help their nervous system feel safer and more regulated?

Yes. Small, repeated practices are often more useful than grand solutions. Helpful starting points can include:

• Slow, extended exhalations. Breathing out a little longer than you breathe in can help the body settle.

  
  

• Grounding through the senses. Notice five things you can see, four you can feel, three you can hear. This can help bring you back into the present.

  
  

• Movement. A short walk, stretching, shaking out tension or even standing up and changing rooms can help shift a stuck state.

  
  

• Supportive connection. Talking to someone safe, sitting near another person, stroking a pet or hearing a calm voice can all help the nervous system settle.

The key is not to force yourself into calm, but to experiment and notice what helps your system feel a little more settled.

How does connection with other people influence the nervous system, and why does feeling safe with someone matter so much?

Human nervous systems are deeply shaped by relationship. Feeling safe with another person can help us regulate more effectively than trying to do it alone. A calm, attuned presence can reduce threat and help the body come back towards balance.

This is why the same level of energy can feel very different depending on context. In safety, activation may feel like excitement, playfulness or motivation. In danger, similar activation may feel like fear, panic or fight-or-flight.

For someone who often feels anxious, exhausted, detached or “stuck”, what would you want them to know?

That these experiences often make sense in nervous system terms, and that change is possible. You are not lazy, broken or failing. Your system may be doing its best to protect you, even if the pattern is no longer helpful.

Psychoeducation can be a good first step. Learning to recognise your states, noticing your triggers and gradually building a small toolkit of regulating practices can help you feel more agency over time. The goal is not perfect calm all the time. It is to become better able to notice where you are, understand what is happening and find your way back.