Understanding Shock Trauma Through Lived Experience: What Happens in the Brain During Acute Trauma

Kirsty Richardson
Nov 23, 2025
8 min read

This article is a little different from what I normally write. I want to share my experience of shock trauma to help explain what happens in the brain during acute, overwhelming danger, particularly the reactions to it that are often misunderstood.

First, it's important to note that trauma can take different forms:

Shock trauma: Immediate life-threatening situations, such as accidents and assaults.
Complex trauma: Repeated or prolonged exposure to harm, such as ongoing childhood abuse or long-term relational trauma.
Vicarious or secondary trauma: Experiencing trauma indirectly, for example, witnessing or learning about traumatic events affecting someone close to you. This can trigger similar nervous system responses as direct trauma, even if you weren’t physically at risk.

Medical Shock

Medical shock is a physical, life-threatening condition caused by injury or illness, where the body can’t deliver enough blood and oxygen to vital organs and can quickly become fatal without medical intervention.

Psychological Shock

Psychological shock (the focus of the article), on the other hand, is an acute stress response to a sudden traumatic event.

While psychological shock isn’t immediately life-threatening in the same way medical shock is, it can have severe longer term consequences to mental wellbeing if not dealt with in an effective and timely way.

The Moment Everything Changed

It was an icy morning. I reluctantly scraped the ice off my windscreen, got into my car, and set off home from work as usual. About ten minutes into the journey, I noticed a woman standing beside a crashed car. I realised later that she was also standing by a man. They both seemed physically okay, and her car was safely off to the side of the road. Another car car was parked on the other side of the road.

The pull to stop was strong, so I turned my car around and parked safely. As I walked up to them, I asked if they were alright. They both reassured me that they were managing the situation.

As I was getting ready to leave, a blue car suddenly appeared and skidded on the black ice that caused the orginal accident. It slammed into the car on the opposite side of the road with deafening force and then veered directly towards us.

As the blue car hit the stationary vehicle, time seemed to slow down.

The first thing I registered was the intense fear in the woman’s eyes as she ran.

Logically, you’d expect you would run too – that you’d react instantly when a car is coming toward you, same as you might expect a person to run or fight their way out of an assault. But that's not always how the brain reacts to shock trauma.

The Brain’s Immediate Response: When Survival Takes Over

As the car veered towards us, it felt as though my brain partially shut down. There was no conscious decision involved, only survival instinct. It felt like the world slowed right down, and it became really difficult to respond logically and quickly.

In extreme threat, the brain assesses instantly:

Can I fight my way out of this situation? Can I run away? Or are neither options possible? Otherwise known as 'fight, flight, or freeze'. The process is actually more complex involving several possible pathways: Freeze, Flight/Fight, Fright, Flag (shutdown) and Faint. See more https://drarielleschwartz.com/the-neurobiology-of-trauma-dr-arielle-schwartz/

NB: Although these survival responses are often described in a specific sequence, the nervous system quickly chooses whichever state seems most likely to keep the person alive in that specific moment, which is why different people can react in completely different ways during the same event. This is also why someone may enter a more extreme shutdown pathway (such as flag), while another person in the same situation may go straight into flight or fight, the body does not necessarily follow the stages in order.

This assessment is not a conscious decision; it's a neurobiological reflex, and it's coordinated through various parts of the brain:

Amygdala: Detects danger within milliseconds
Periaqueductal gray: This determines whether to fight, flee, freeze, or collapse
Prefrontal cortex: This is the logical part of your brain that usually reasons what to do in any situation; however, this part of the brain goes partially or fully offline when the threat is overwhelming.

Dual Awareness During Freeze

During the incident I had dual awareness, a strange split where one part of me was in freeze, and another part was watching it happen, trying to keep my prefrontal cortex online so I could stay functional. The advantage I had from my training in trauma was my awareness of what was happening and what I could do to try and keep my brain from shutting down even more, but I had no choice in how my brain initially reacted. Whilst impaired, this allowed me to take action where others were struggling.

Freeze in Action: Why People Don’t React as Expected

Despite the freeze state I was in, I moved toward the crashed car. The anticipation of what I'd find, alone was traumatic. When I opened the door, I found the driver initially unresponsive. My first-aid training felt patchy. In freeze state, as mentioned earlier, the prefrontal cortex can temporarily partially or fully shut down, making learned skills harder to access.

I saw others appear at the scene in similar shock states. I asked for help from a passer-by but he was unresponsive. Even those who hadn’t seen the crash were showing what appeared to be freeze responses: blank expressions, shut-down posture, and minimal engagement.

Research on the bystander effect supports this observation: when people witness an emergency, reflexive responses such as freeze, avoidance, or inaction can take over, even in people who want to help. These responses are partly driven by subcortical brain mechanisms and personal dispositions, meaning that freeze is not a conscious choice. You can read the full study here: Ruud Hortensius & Beatrice de Gelder, From Empathy to Apathy: The Bystander Effect Revisited (PMC6099977).

I held the man’s hand and managed to speak just enough to assess the level of emergency. My brain kept switching on and off like a flickering light, moments of clarity followed by moments of shutdown. My attention narrowed; people seemed to appear and disappear at the edges of my vision as though they were out of the frame and far away. I realised my phone was in my car, which at this point felt really far away from me. I was functional enough to ask a bystander to call for an ambulance. The pungent smell of the chemicals from the engine hit my lungs and reminded me to check for further danger.

After some time, I noticed I was starting to zone out more and more and felt very sleepy. Despite my best attempts to keep my prefrontal cortex fully online, I knew I needed to leave to regulate myself, so once paramedics arrived I stepped away.

Understanding the Neurobiology of What Happened

During a traumatic incident, the body generates energy to fight or flee, even if the nervous system temporarily freezes or shuts down.

If the energy cannot be discharged via fighting or running, the energy remains stored in the body. When animals are traumatised, they instinctively tremble, shake, or move to release this energy in order to complete the survival response. As humans we may start this process via trembling, but if we don't complete the process effectively, the energy can become trapped and can lead to prolonged trauma, hypervigilance, and eventually can turn into Post Traumatic Shock Disorder (PTSD). As Bessel van der Kolk was quoted as saying, "Healing happens in the presence of an empathic witness," It is also important as humans that we get support after a traumatic incident to reduce the impact of the trauma after the event.

We will often do things instinctively, like talk over what happened and seek out a supportive person we can co-regulate with but sometimes things can get in the way of these processes and effective co-regulation may not be available.

When I got home, I immediately documented everything verbally. This helped for two reasons:

Kept my prefrontal cortex active, reducing memory fragmentation.
Prevented dissociation from the event, which can lead to intrusive symptoms later.

I could feel the unprocessed energy in my system very acutely. This is because the body prepares to run or fight even if it goes into a freeze state, but if escape isn’t possible, that energy remains stored.

So I literally shook all parts of my body to shake off the stored trauma. This was me consciously pushing my body to complete the motor sequence it couldn’t finish during the event.

I started getting olfactory flashbacks later in the day (smell of the engine).

Olfactory flashbacks (are sudden, vivid recollections triggered by smells can occur immediately after trauma. Smells are strongly linked to the limbic system, which processes emotions and memory. This is why sensory cues can trigger flashbacks long after the event.

Responses in High Empathic People

When I got home, it felt as though I had been in the accident myself. I experienced pain in my body, especially in my head and neck, along with nausea. Whilst I had experienced a direct threat to my own life and the shock of the accident, I also experienced vicarious trauma.

Empathy plays a key role in how we experience trauma, both directly and vicariously. People with high empathy often experience something called a vicarious somatic imprint. This happens because of brain cells called mirror neurons that fire when we perform an action ourselves and also when we observe someone else performing it. They basically allow us to mirror the experiences of others in our own brains and bodies.

In practical terms, this means that when you witness someone else in distress, your brain can react as if you were experiencing the trauma yourself. Highly empathic people tend to experience this effect more strongly, which can make witnessing someone else’s distress feel very intense.

In trauma related to sexual assault or intimate partner abuse, this can amplify automatic survival responses such as freeze or fawn. Fawn responses (where the body appeases or placates a threat) can also be influenced by empathy, as the brain instinctively seeks to reduce harm. (See links below for more information on fawning and assault).

It’s important to be aware of this if you are in a traumatic situation and called upon to help others, as well as if you are hearing about something traumatic: other people’s responses can imprint on our nervous system, which requires us to manage the psychological trauma as if it were our own.

What to Do After Experiencing or Witnessing Trauma

It’s common to feel guilt or shame for not reacting well or at all in shock trauma. However, freeze and flag are not conscious choices, they are neurobiological responses and we do not get to decide how our brains react in an emergency situation.

It is also important to recognise that everyone's brains will react slightly or in a markedly different way to the same traumatic incident for various reasons.

Early management is crucial to reduce prolonged trauma:

Co-regulate with someone emotionally safe: A trusted friend, family member, or support person can help your nervous system settle.
Talk it through with a trained trauma therapist if possible: A professional can help you process the event safely and provide tools to regulate your nervous system.
Discharge energy (If you are able to): Shaking, pacing, or gentle movement completes the fight/flight response and reduces the risk of long-term trauma.
Rest and monitor- Rest for as long as needed and monitor how your body responds over the next few days.

Signs that trauma may be present and needs attention:

Intrusive memories or flashbacks
Flashbacks- (smells, sounds, images)
Heightened startle response or hypervigilance
Avoidance (eg. of the environment the incident happened)
Feeling numb emotionally/ difficulty connecting to others
Sleep disturbance/ nightmares
Anxiety or panic

Addressing these as soon as possible is important to prevent prolonged dysregulation and promote recovery.