Research has revealed that trauma produces actual physiological changes, including a recalibration of the brain’s alarm system, an increase in stress hormone activity, and alterations in the system that filters relevant information from irrelevant.
We now know that trauma compromises the brain area that communicates the physical, embodied feeling of being alive. These changes explain why traumatized individuals become hyper-vigilant to threat at the expense of spontaneously engaging in their day-to-day lives. They also help us understand why traumatized people so often keep repeating the same problems and have such trouble learning from experience. We now know that their behaviors are not the result of moral failings or signs of lack of willpower or bad character—they are caused by actual changes in the brain.
Bessel van der Kolk
From Peter Levine’s “Healing Trauma.”