What's the connection between trauma and nervous system dysregulation?

Trauma often creates lasting nervous system changes. As Dr. Bessel van der Kolk describes in The Body Keeps the Score, traumatic experiences can get stuck in the body, leaving the nervous system perpetually on alert for danger that’s no longer present. This shows up as hypervigilance, exaggerated startle response, difficulty feeling safe, and triggers that activate survival responses. Trauma work often focuses on helping the nervous system complete interrupted stress responses and learn that the danger has passed.