When the Brain Can’t Let Go: Understanding How Trauma Rewires Our Stress Response
The brain doesn’t always know the difference between what is happening right now and what happened years ago. When the nervous system has learned to fear something, it can continue to respond as though the danger is still present, even long after it has passed. This is not a character flaw. It is neuroscience.
In September 1999, Stan and Ute Lawrence were driving to a business meeting in Detroit when dense fog caused a catastrophic accident. Stan slammed on the brakes, and moments later an 18-wheeler went flying over their car. They ended up trapped in car number 13 of an 87-car pileup. Both survived, but their brains experienced the same traumatic event in very different ways. Their story, discussed in Bessel van der Kolk’s The Body Keeps the Score, illustrates an important point: trauma does not just affect what happens to us; it can change how our brains process stress, threat, and safety (van der Kolk, 2014). Trauma can overwhelm our normal processes and affect fear responses, memory, and how we interpret our environment (Rousseau, 2026).
This topic is deeply personal as well as professional for me. Growing up working with children from kindergarten through eighth grade, I have seen how stress and trauma can affect a child’s ability to learn, trust, and behave. I have observed children whose nervous systems seemed to remain in a constant state of threat, making it difficult for them to focus on the learning and growth they needed. A child who acts out in class may have a nervous system still preparing to fight or freeze. A quiet, withdrawn child may be dissociating or protecting themselves through numbness. Understanding this changes how we view behavior. Stress responses are not necessarily failures of character; they can be evidence that someone’s brain has experienced something it struggled to process.
Stan and Ute demonstrate just how differently people can respond to the same traumatic event. When Stan relived the crash, his amygdala, which functions as part of the brain’s alarm system, became highly active (van der Kolk, 2014). His brain responded as though the danger were happening again. Ute’s response was very different. When she recalled the trauma, her mind went blank and brain activity decreased significantly. Both responses were real, and neither was a choice.
The amygdala is part of the limbic system, which includes structures such as the amygdala, hippocampus, and hypothalamus that help regulate emotions, memories, and stress responses (Rousseau, 2026). When the amygdala detects a potential threat, it can activate the fight, flight, or freeze response before the conscious mind has time to process what is happening. This can make it difficult to distinguish between an actual threat and a reminder of a previous one (Rousseau, 2026; van der Kolk, 2014). For someone like Stan, certain sounds, smells, or even the feeling of being trapped could potentially trigger a trauma response even when he consciously knows he is safe.
The hippocampus also plays an important role because it helps organize experiences and memories into a coherent narrative. Trauma and chronic stress can interfere with this process, which may help explain why people experiencing trauma sometimes have difficulty recalling the timeline of an event while remembering seemingly insignificant details, such as a song, clothing, or a particular location (Rousseau, 2026). The hypothalamus is also involved in regulating functions such as sleep, breathing, arousal, and the body’s response to stress. Chronic stress can therefore affect much more than someone’s emotions; it can affect the way their entire body functions (Rousseau, 2026).
Ute’s dissociation is another example of how the brain can respond to overwhelming stress. Van der Kolk (2014) describes dissociation as a central part of trauma. When stress becomes unbearable, the mind can disconnect from sensations and emotions. These responses may be protective during an immediate threat, but when they continue long after the danger has passed, they can interfere with daily life. Research also shows significant involvement of the limbic system, amygdala, and hippocampus in PTSD. At the same time, we need to be careful about what the research actually tells us. For example, researchers cannot always determine whether changes such as reduced hippocampal volume contribute to PTSD or occur as a result of it (Rousseau, 2026). Understanding trauma means recognizing what we know while also acknowledging what we still do not know.
Understanding why trauma responses occur does not excuse harmful behavior—it contextualizes it. A child who becomes aggressive because their nervous system is overwhelmed still needs boundaries and support, but understanding the underlying trauma allows us to respond with more compassion and realistic expectations. For professionals working with traumatized individuals, including social workers, teachers, police officers, probation officers, and mental health professionals, this perspective matters. Instead of only asking, “What is wrong with this person?” we can also ask, “What happened to them, and what is their behavior communicating?”
Recovery is also more complicated than simply “getting over” trauma. Van der Kolk (2014) describes recovery as a process of reintegration, while trauma-informed approaches emphasize therapy, safe relationships, mindfulness, and other practices that can help individuals regulate their stress responses. Even something as simple as deep breathing can help activate the body’s calming systems and support regulation (Rousseau, 2026). Healing does not erase what happened, but it can help the brain and body learn that the danger is no longer happening.
This understanding also needs to extend to the professionals who work with trauma. We cannot pour from empty cups. We cannot remain fully present for others if our own nervous systems are constantly overwhelmed. Self-care is not a luxury when working with trauma; it is part of being able to do the work. At the same time, the responsibility cannot fall entirely on the individual. Organizations also have a responsibility to provide support through peer support, confidential mental health resources, and education about secondary traumatic stress.
Stan and Ute survived the same traumatic event, but they experienced its effects differently. Their story reminds us that there is no single way that trauma looks or affects the brain. What may look like aggression, withdrawal, poor concentration, or emotional numbness may actually be a nervous system trying to protect itself.
For me, understanding the neurobiology of trauma changes the way I look at behavior. It does not mean removing accountability or assuming that every behavior is caused by trauma. It means slowing down enough to ask what might be happening beneath the behavior. Trauma can trap people in moments their brains have not fully recognized as finished. As professionals, our job is not to erase those experiences, but to help create the safety and support necessary for people to move forward.
References
Rousseau, D. (2026). Module 3: Neurobiology of trauma [Online module]. Blackboard at Boston University.
van der Kolk, B. A. (2014). The body keeps the score: Brain, mind, and body in the healing of trauma. Viking.