One of the classic books on the processes underlying trauma “Waking The Tiger” by Peter Levine provides a comprehensive introduction to the mechanisms of the nervous system, and levels of response connected to “fight and flight”, and “freeze”.
Peter Levine began his work in the 1960’s when he became interested in the mind-body connections. After graduating in medical biophysics, he spent time in Esalen, California, and met Dr. Ida Rolf (founder of Structural Integration) and Fritz Perls (founder of Gestalt Psychotherapy). In the early days, he was referred a patient who entered a deep state of relaxation, triggering a release process where she returned to the traumatic event and was able to access a fight & flight response, where previously she had been frozen. This re-regulation of the nervous system, led Peter Levine to develop Somatic Experiencing – a therapeutic method for re-regulating trauma.
This book provides a good introduction and foundation around understanding trauma, its symptoms and underlying processes, for both practitioners and anyone interested within this field.
Here’s a link to the book and further resources below.