Why Trauma Changes the Nervous System
“Why do I feel on edge, even when I know I am safe?” “Why does my body react to something that I know isn’t happening right now?” These are very common and understandable questions people can have after experiencing trauma. Most people understand the emotional changes that can follow trauma, but what can catch us off guard are the physiological effects that can linger long after the trauma is “over.”
Here are common physiological symptoms people can experience after a trauma:
Trouble relaxing or restlessness
Sleep changes/difficulties
Always feeling “on edge” or tense
Feeling disconnected from yourself, others, or your surroundings
Jitteriness or shakiness
Chronic body aches and pains, like muscle tension and stomach issues
What’s important to know about these symptoms is that they don’t reflect weakness; they are a sign that your mind and body have learned an important lesson- the world can be dangerous, I need to be ready. Experiencing trauma can physically alter the way your brain and nervous system detect and respond to potential danger.
What Does the Nervous System Do?
It’s helpful to first understand a few basic things about the nervous system. First, its job is simple – to keep us alive. The nervous system is constantly adjusting and regulating our heart rate, breathing, muscle tension, digestion, and temperature, and even plays a large role in regulating our attention, sleep/wake cycles, and emotional responses.
While its basic functions are essential to our survival, the tradeoff is that it doesn’t mean it’s always working to keep us comfortable. In fact, when the threat response system is activated, via real or perceived danger, things can actually get quite uncomfortable, physiologically.
What Happens During a Traumatic Experience?
Most of us have heard of the fight/flight/freeze/appease response. This is the automatic response we experience when our nervous system picks up that something might be threatening to us. It’s incredibly useful when danger is present but becomes problematic when our systems become too sensitive after danger has passed.
During a traumatic event, the brain and body instantly prioritize survival. Again, it’s important to remember this is not a conscious choice we make. Our nervous system very quickly takes in all the information it can about the situation and then decides which response is most likely to help us survive. Remember those basic functions? Here is where that physical discomfort comes in – adrenaline and cortisol are released, our heart rate and breathing increase, our muscles tense, our digestion slows or stops, our attention becomes narrowed to the threat. Our brains are also hard at work taking in details and making associations. It’s assessing things like what happened, what my environment looked/sounded/smelled like, how my body felt, and what happened right before the danger.
Why Can the Alarm System Stay “On”?
Here is where things have the potential to become problematic after the danger has passed. Our nervous system is constantly learning from our experiences, and that is something we can’t turn off. Depending on a variety of factors, the nervous system can make overgeneralized associations between the trauma and its accompanying situational details. This means that when we experience cues (physical or environmental) that resemble those we have associated with the original trauma, our threat response system gets activated, even though no actual danger is present. This is our brain’s way of trying to protect us. Unfortunately, our nervous system isn’t perfect and can’t always accurately distinguish between “this is dangerous” and “this reminds me of something that was dangerous.”
Trauma Triggers Aren’t Always Obvious
It doesn’t have to be a big or obvious reminder either. Of course, people, places, and situations that closely resemble those associated with the trauma are likely triggers. But it can also often be something sensory and just outside our awareness – like a smell, a sound, a taste, or even a physical sensation itself, that can trigger the threat response. It’s important to recognize that you also don’t have to consciously remember all or even most of the trauma for this to happen. Your nervous system can still respond to cues that became associated with danger.
Some examples might help illustrate this:
After a car accident, someone experiences anxiety every time they get into a car. Or, they notice increased heart rate when they pass the street on which it happened
After an assault at a bar, someone feels on edge or unsafe at other bars, restaurants, or crowded areas. Maybe the smell of cigarettes is a trigger, or even the type of music that was playing
After combat exposure, someone becomes extremely tense and fearful around loud or unexpected noises
Childhood trauma can cause heightened sensitivity and emotional reactivity to conflict, criticism, or rejection in adulthood
There is a cluster of symptoms associated with post-traumatic stress specifically for the nervous system and when it becomes overly sensitive. These are called “hyperarousal” symptoms, and they include hypervigilance (very aware and watchful), exaggerated startle response (“jumpy”), irritability, anger, racing heart, muscle tension, difficulties with sleep and concentration, restlessness, and a feeling of dread or foreboding.
In the face of real danger, these symptoms make a lot of sense (and relate directly to those basic functions of the nervous system). If we were to put this into a conscious thought it would sound like, “Well I’ve learned that bad things can happen unexpectedly. Better to stay alert and ready. Just in case.” However, this becomes exhausting and problematic for day-to-day life.
When the Nervous System Shuts Down
Although this heightened state is not uncommon post-trauma, sometimes the opposite can happen. While what we described above fits more of the “fight or flight” responses, the nervous system can also change by adopting a more “shutdown” response (e.g., “freeze”). This can look like emotional numbness, feeling disconnected or detached from yourself, others, or your surroundings, limited range of emotions, and excessive fatigue. This is our system’s response when it feels that escape or fighting isn’t an option.
Why Avoidance Can Keep the Cycle Going
When someone continues to experience these symptoms post-trauma, it can be frightening, confusing, embarrassing, and exhausting. Therefore, a very common and understandable way to try to manage it all is to simply avoid the things we know or expect to cause these unpleasant symptoms. Avoiding something that causes fear or discomfort is also highly reinforcing due to the immediate relief it provides. The problem here, though, is that although the relief is immediate, it is also temporary. Each time we avoid something, we not only reinforce what we already believe, we also prevent ourselves from learning something new. Instead of learning “I can do this. This can be safe. This is a reminder of danger, not current danger,” avoidance perpetuates the opposite beliefs. Over time, this can make one’s world very small and unfulfilling.
The cycle: Trigger → nervous system alarm → anxiety/discomfort → avoidance → immediate relief → brain learns “avoiding worked” → increased sensitivity next time
This is one reason trauma-related avoidance can be so difficult to break. From the nervous system’s perspective, avoiding the situation worked: the threat response went down.
Is your nervous system broken?
No. It is responding in a normal way to a very abnormal experience.
Can I “rewire” my nervous system?
In a sense, yes. The nervous system is adaptable. In the same way that it adapts to new information brought by trauma, it can adapt to corrective experiences. The changes brought by trauma don’t necessarily have to be permanent. With appropriate treatment and good support, we can learn to respond differently to trauma reminders. Trauma-focused therapy should focus on understanding symptoms, identifying triggers, developing skills to help with emotional and physiological regulation, reducing avoidance, examining any beliefs about the trauma keeping you stuck, and gaining new experiences of safety and coping. The goal isn’t to eliminate your threat response, but to build greater flexibility and awareness.
Treatments such as Prolonged Exposure (PE) are based in part on the idea that the brain can learn through new experiences. Rather than continuing to organize life around avoiding reminders of trauma, therapy can help you gradually and safely approach what you've been avoiding so that your brain has an opportunity to learn that the danger is no longer present.
When Should You Seek Help?
Sometimes it can be hard to know when to seek help. Don’t overthink it. If you’ve found yourself here and related to any of the symptoms discussed, it would probably be beneficial to speak with a professional about your experience. If you notice things like chronic sleep troubles, withdrawing from relationships or things you used to enjoy, feeling disconnected, trouble concentrating with school or work, persistent anxiety or anger, or planning your life around things you can and can’t do or places you can and can’t go, reaching out to a trauma-informed provider is a good first step.
Trauma Can Change the Nervous System—and So Can New Experiences
Yes, trauma changes the nervous system. But so can appropriate treatment and safe corrective experiences. Although the changes are protective in nature, they can continue to cause disruption long after the trauma has ended. Understanding your symptoms can help lessen shame and increase willingness to challenge yourself in the service of getting your life back. If trauma symptoms are affecting the way you live, work, or connect with others, therapy can help. You don't have to figure it out on your own.
