How trauma affects your stress response & how you can heal

Have you noticed that after a bad night’s sleep you’re more likely to snap at a loved one? Do you jump out of your skin at loud noises, or sudden movement? As menstruation creeps closer, are you more reactive to perceived criticism?

Our ability to regulate and respond during times of stress - also known as our window of tolerance - is elastic, and informed by both current circumstances and our history.

The window of tolerance is a term coined by clinical professor of psychiatry, Dan Siegel. It’s the state in which you’re able to respond to stressors calmly without reactivity. When you’re inside it, you’re able to stay open and curious. But when a stressor is big enough, you move outside of your window of tolerance - slipping into fight, flight or freeze. 

Your amygdala detects fear. When it rings the alarm bell for a threat, the hypothalamus receives the signal and kicks the sympathetic nervous system into gear, triggering the fight or flight response. Alongside the amygdala, the prefrontal cortex - the part of our brain responsible for conscious thought, helps process and regulate fear.

A history of trauma sensitises your stress response, narrowing the window of tolerance. As humans, we’re wired for protection and adverse past experiences teach our nervous system to be vigilant, scanning for danger to keep us safe. People who have experienced trauma may find they’re more responsive to loud noises, more prone to shut down, or disassociate, or find it hard regulating their emotions. 

If that’s you, it may be hard not to judge yourself - but it’s important to remember you are not broken. You experienced really challenging events and in response to that threat, your body is doing exactly what it is programmed to do for survival - ring the alarm bells hard and fast.

But - that doesn’t mean you have to continue living life on a knife edge, continuing to scan for danger, or numbed out in response to difficult feelings. “Healing is possible, but the pre-requisite is safety,” explains Carole Bradshaw, IMI Core Process Psychotherapist.

What’s above and below your window of tolerance?

Hyperarousal sits above your window of tolerance. When you’re in a state of hyperarousal, your sympathetic nervous system (SNS) is activated – also known as the fight or flight response.

Hypervigilance is a symptom of hyperarousal. It’s when you’re on alert, looking for dangers and is common among those with neurodiversity or a history of trauma.

You’ll notice if you’re in a state of hyperarousal because of its bodily experience – it feels high valence, active and intense. There’s often a lot of uncontrolled energy in this state.

When you dip below your window of tolerance, you enter hypoarousal. A key example of this is disassociation – in which you might feel numb, floaty or separate from your body. Space between you and other people might warp. It might be hard to string a sentence together. This is the freeze response – like a rabbit in headlights. 

The role of your vagus nerve: an introduction to polyvagal theory

The vagus nerve is key for your capacity to stay inside your window of tolerance.

It is the longest cranial nerve in your body, and is integral to the function of your nervous system. Its nickname ‘the wandering nerve’ comes from its Latin roots, vagus which translates to ‘wandering’.

It connects to major organs like the heart, lungs and gut and carries messages between the brain and the body, in both directions. Messages from the brain to the body affect our breathing, heart rate, facial expressions, voice, mood, immunity and digestion. Likewise, messages from the body (like slowing your breathing) send information to your brain – letting you know you’re safe.

Polyvagal theory, created by professor of psychiatry Dr Steven Porges, centres around the vagus nerve. In this theory, there are three different states – your sympathetic nervous system state and the dorsal vagal and ventral vagal pathways – which relate to the two main branches of the vagus nerve.

The ventral vagal and dorsal vagal branches are activated by the parasympathetic nervous system.

In the ventral vagal state, we feel connected to others – we are inside our window of tolerance.

The dorsal vagal and sympathetic nervous system have different attributes depending on whether you’re feeling safe or unsafe.

When you’re feeling safe and in a sympathetic nervous system state, you might feel playful or energetic. When you’re feeling unsafe, you enter hyperarousal.

A safe presentation of the dorsal vagal pathway might look like the state of mind achieved during meditation, or a massage – dreamy, blissed out and liminal. When feeling unsafe, you enter hypoarousal - the freeze state.

There are also hybrid states, where two pathways are activated at once. For example, when the ventral vagal is blended with the sympathetic nervous system, we find ourselves in a state of flow and play.

What narrows your window of tolerance?

Everyone has a different sized window of tolerance. It is a fluid ever-changing thing, and physical factors including poor sleep, nutrition (like low levels of B12, iron or having low blood sugar) or neglecting your self-care, can have an impact on a day to day basis.

Other factors that narrow your window? Neurodivergence, OCD, chronic pain, chronic stress and having too many demands on your energy.

Traumatic events have a big impact. “Trauma is not just a story, it is somatic,” says Carole Bradshaw, IMI Mindfulness Psychotherapist.

Trauma is held in the body. It creates patterns of response in your nervous system, which are replayed when you encounter future stressors. Your alarm system becomes more sensitive - looking out for danger, to keep you safe. 

At times, avoiding stressful situations may feel like the only coping mechanism you have- but doing this can reinforce to your nervous system that perceived threats are real and confirm a feeling of danger.

Using drugs and alcohol is a common coping strategy for managing difficult feelings that arise following trauma. It’s often used as a way to numb hyperarousal, or to experience something other than hypoarousal. Though the altered state achieved using substances can provide temporary relief, it doesn’t provide healing in the long term, and narrows your window of tolerance.

When you enter into therapy, you may find that you feel worse initially, as you begin to feel and process emotions that may have been suppressed for a long time. This narrowing of your window is only temporary – and after this initial phase you’ll begin to build resilience and expand your window.

Strategies to expand your window of tolerance

The key to expanding your window of tolerance is noticing when you’re activated, whether that’s hyperarousal or hypoarousal, and then using techniques to move back to a healthy baseline.

“It’s not about being calm all the time – it’s about building the resources to cope when you move outside of your window of tolerance,” says Carole.

“Top-down strategies like CBT, which work with the mind first, don’t tend to work well when you’re struggling to regulate, as they require too much mental activity, which is difficult to access when you’re in hyper or hypoarousal. The most effective methods are bottom-up,” says Carole.

Bottom up methods work with the body first. They include mindfulness, breathwork, art, dance and somatic therapy.

 “These approaches focus on grounding and creating safety in the body, which is key for expanding your window of tolerance. In a therapeutic context, I might explore small stressors with a client – those close to the frame of your window of tolerance. We’re not going for a 10/10 stressor, but we are building confidence and teaching your nervous system to regulate after experiencing stress.”

What might a gentle expansion of your window of tolerance look like?

If you’re scared of spiders, you don’t want to start with a 10/10 stressor like going to the zoo and handling a tarantula. You might start by looking at photos of spiders, and touching those photos. When that feels comfortable, you might build on that by looking at a small house spider, and so on.

“We want to teach your nervous system that stress can happen and you can find your balance again. In sessions, sometimes what I do is oscillate between a little activation, and then something resourcing. This builds flexibility in the nervous system and brain. We don’t want to push too hard, if you move too far into activation and become overwhelmed, this can be counterproductive,” says Carole.

Coming back to your window of tolerance after activation

Trauma informed work begins with the body – in feeling, rather than intellectualising positive or negative feelings.

Humming is a tool that helps soothe the vagus nerve, activating your parasympathetic nervous system and helping your body calm. “I use Bhramari pranayama, which is a technique from a yogi practice. It helps lower your heart rate and is a simple, powerful way to ease anxiety and get you ready for bed,” says Carole.

Similarly, breathwork is an always accessible tool to help soothe your vagus nerve. A simple technique is taking a deep breath in, and slowly exhaling for longer than you inhale.

“During sessions, I use grounding practices, such as body-based breathing, or bringing awareness to sensation in the client’s body. These practices work particularly well if a client is able to be in nature, barefoot on grass or sand, but this isn’t always possible. Just looking at nature (even if it’s a houseplant) can help support the grounding process. When you’re alone, you might find it helpful to get into nature or go for a walk, focusing on the contact between your feet and the earth,” says Carole.

“In sessions, gently encouraging the person I’m working with to feel their feelings, rather than suppressing them is key for expanding the window of tolerance. If you fear your emotions because they feel overwhelming, your nervous system learns that emotional equals danger. By working with your feelings in a safe, regulated way, you learn to allow the emotion to rise up and pass. This teaches your nervous system that you can feel emotions and still be safe,” she adds.

“Once the trauma has been processed on a somatic level, and your nervous system feels safer, there is more space for processing past events cognitively and exploring the story of what has happened.”

The importance of safe relationships

“From a neuro-biology perspective, safe relational experiences are really important. This is also known as co-regulation, and it’s one of the most powerful ways to expand your window of tolerance,” says Carole.

If trauma, or relational rupture has occurred in your past, you’re left in an overwhelmed state, trying to muddle through alone. You learn to use adaptive defences like dissociation, passive aggression, black and white thinking, projection, repression, to protect yourself from challenging feelings.

In that process, you learn that relationships and big feelings are dangerous – they’re linked to loss, or traumatic events.

“When working with clients, I walk with them as they explore difficult moments, reassuring them and remaining present as I learn about their inner world. I learn a lot, not only from what is being said, but what isn’t being said. Transference and counter transference is often a big part of the process.”

Transference is the process by which a client projects feelings about significant people from their past onto a therapist – this might be either through idealisation of an imagined person (how they wished their parent or past romantic relationship treated them) or through a negative lens (unhealed wounds, unmet needs coming to the surface). Countertransference describes the thoughts, feelings and sensations that arise in the therapist in relation to their client, which informs the way the therapist is able to understand and respond to them.

Done skilfully, exploring transference and countertransference can provide important avenues for healing – as your nervous system can experience the possibility of safety, even when past triggers or wounds arise. 

In summary

Traumatic events in your history are held in the body, and re-experienced by your nervous system as though they’re playing out in the present. The body keeps the score –  the title of Bessel van der Kolk’s seminal book summarises this understanding neatly.

The effects of these events can touch our daily lives, and narrow our window of tolerance, which can dictate how we interact with the world around us.

Building resilience to stress and expanding our window of tolerance allows us to gain confidence and a sense of safety as we move through our lives. If you’re looking to expand your window of tolerance and explore past events which still touch your present day, it’s important to find a trauma-informed psychologist or psychotherapist.

“It’s the feeling of safety that allows the window of tolerance to expand,” says Carole. So, finding a practitioner who is able to downregulate an alarm system sensitised by trauma is really key to the healing process. 

References 
R J Walker & SouthWest Trauma Training, Polyvagal chart, 2023.
The polyvagal institute, What is polyvagal theory?
The polyvagal institute, What is the vagus nerve?
M Di Giuseppe, J C Perry, The hierarchy of defense mechanisms: assessing defensive functioning with the defense mechanisms rating scales Q-sort, 2021.
Roamers therapy, Shifting between survival modes: understanding trauma through polyvagal model.
National institute for the clinical application of behavioural medicine, NICABM Experts: Stephen Porges, PhD.
National institute for the clinical application of behavioural medicine, What’s happening in the nervous system or patients who ‘please and appease’ (or fawn) in response to trauma? With Stephen Porges, PhD.
K J Ressler, Amygdala activity, fear and anxiety: modulation by stress, 2010.