Trauma has considerable impact on our neurobiology, and there are actual physiological changes that can accompany trauma. To start with, trauma involves an intense activation of our stress response. The HPA axis (hypothalamus, pituitary gland, adrenal gland) mediates our brain’s stress response. In the face of stress, the HPA axis is activated. It sends out stress hormones, known as glucocorticoids. These serve to activate the autonomous nervous system, making our heart pump faster, our breath more rapid and shallow, and blood rush to our large muscle groups from our small muscle groups. This allows our body to respond rapidly to threat.

In normal circumstances, our parasympathetic nervous system acts to restore this system to a resting state, allowing our body to recover from the stress reaction. However, with trauma, the whole stress system can be thrown out of whack, causing abnormalities within the HPA axis, and keeping our autonomic nervous system (specifically the sympathetic nervous system) on overdrive. This has the effect of wearing down the body, compromising the immune system, and putting undue stress on many parts of the body’s regulating systems. In childhood when the brain is not fully developed, severe trauma can interfere with the brain’s actual development, causing long-term damage.