Psychological trauma is among the most devastating of conditions. Though classified as a mental health disorder, it affects the body at the most fundamental levels. This monograph traces the physiological roots of posttraumatic stress disorder in the body's many systems: The brain, the autonomic nervous system, the endocrine system, and the many organs they control. It weaves together the most current research from many different scientific fields. These include: - Epigenetics - Neuropsychology - Developmental Psychology - Evolutionary Biology - Immunology - Polyvagal theory - Biofeedback - Energy Psychology - Epidemiology - Memory Reconsolidation. This up-to-date review of the science shows how when we are traumatized, especially at an early age, changes occur deep in the brain. These are reinforced by neural plasticity, our brain's ability to rapidly add new synaptic connections. Over time, these intensify the symptoms of PTSD, often leading to disabling personal limitations. This monograph also reviews the evidence from the new field of memory reconsolidation. This shows that under very specific conditions, fear-based memories may be revised by the brain. The new therapies emerging in the field of energy psychology, especially EFT (Emotional Freedom Techniques), are able to quickly neutralize traumatic emotions. This monograph explains the physiological mechanisms behind the efficacy of these novel therapies. Besides discussing several key clinical trials showing rehabilitation of over 80% of PTSD sufferers, it contains many case histories of veterans and others who have made full recoveries using EFT. It is a unique resource for scholars, therapists, physicians and journalists, as well as patients who wish to understand the underlying physiology of stress.