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The biology of trauma
Trauma leaves traces beyond the psyche. The nervous system, stress hormones, gut function, immune signaling, and even gene expression can all be affected, which is part of why trauma can show up as anxiety, IBS, chronic pain, fatigue, insomnia, or a body that simply no longer feels safe inside itself.
Amygdala and fight-or-flight
During traumatic experience, the amygdala becomes highly reactive and pushes the sympathetic nervous system into a fight-or-flight state. Cortisol, norepinephrine, and epinephrine surge to support immediate survival. That is adaptive in the short term. The problem comes when the nervous system stays organized around threat long after the danger has passed.
Chronic or repeated trauma can leave the amygdala hyper-sensitized. The result may be hypervigilance, insomnia, anxiety, difficulty concentrating, and a body that struggles to distinguish past threat from present safety.
Trauma is often remembered not only as a story, but as a nervous system state.
Hippocampus and glutamate
The hippocampus, which helps with memory and emotional regulation, also seems vulnerable in trauma. The original newsletter highlighted glutamate dysregulation and the possibility of excitotoxic stress, where excessive neuronal activity harms brain cells rather than helping them adapt.
This can help explain why trauma survivors may report memory problems, poor spatial orientation, difficulty regulating emotional response, or a sense that recall and presence no longer work the way they used to.
The same article also noted that trauma may influence gene expression through epigenetic change, while neuroplasticity still leaves room for repair. In other words, trauma changes biology, but biology remains capable of change.
Cortisol, stress load, and the gut
Trauma can sustain cortisol elevation and alter broader stress-hormone patterning. When that happens over time, sleep quality, immune function, digestion, blood sugar handling, and recovery capacity may all shift.
The newsletter connected this directly to the gut-brain axis and to IBS in particular. Chronic stress can disturb gut motility, alter microbiome balance, and increase inflammatory signaling, making it easier to understand why trauma histories so often overlap with digestive distress.
Clinical implication: if a patient presents with anxiety, insomnia, IBS, fatigue, and a history of trauma, it often makes more sense to think in terms of shared biology than to treat each symptom as unrelated.
ACEs and long-term risk
Adverse Childhood Experiences, or ACEs, have been associated with a higher risk of later health problems including IBS, depression, and cardiometabolic disease. Early life trauma appears capable of shaping stress regulation, immune function, and gut health over time, which may help explain why some adult symptom patterns are so persistent.
This does not mean a difficult childhood mechanically determines an adult diagnosis. It does mean the developmental environment can become part of the physiology we inherit into adulthood.
A biologically informed healing model
A biologically informed trauma model asks more than whether someone is “stressed.” It asks how nervous-system dysregulation, cortisol burden, sleep disruption, inflammatory load, pain, gut dysfunction, and emotional threat memory are reinforcing one another.
That is why trauma work can benefit from multiple layers of care. Psychotherapy may be essential. So may somatic work, neurofeedback, sleep repair, nutrition, gut restoration, acupuncture, stress-physiology support, and a broader team-based framework. The goal is not to deny the psychological reality of trauma, but to recognize that trauma is carried through biology as well.