The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma

by Bessel van der Kolk

Why is HRV important? When our autonomic nervous system is well balanced, we have a reasonable degree of control over our response to minor frustrations and disappointments, enabling us to calmly assess what is going on when we feel insulted or left out. Effective arousal modulation gives us control over our impulses and emotions: As long as we manage to stay calm, we can choose how we want to respond. Individuals with poorly modulated autonomic nervous systems are easily thrown off balance, both mentally and physically. Since the autonomic nervous system organizes arousal in both body and brain, poor HRV—that is, a lack of fluctuation in heart rate in response to breathing—not only has negative effects on thinking and feeling but also on how the body responds to stress. Lack of coherence between breathing and heart rate makes people vulnerable to a variety of physical illnesses, such as heart disease and cancer, in addition to mental problems such as depression and PTSD.