The neurobiology of PTSD differs from that of a normal response to fear or stress because the symptoms of PTSD continue to occur well after the stress or fear is no longer physically present. Lack of awareness of the sequela of PTSD, however, prevents many from seeking treatment for their symptoms.

PTSD is marked by clear neurobiological and physiological changes, as well as psychological symptoms. The neurobiology is complex, involving dysregulation of neurotransmitters such as serotonin and norepinephrine, as well as the sympathetic nervous system (fight or flight) and HPA axis. Dysfunction in these systems may lead to disturbances in the processes of perception, learning, and memory.

Neurobiological alterations are seen in both the central and autonomic nervous systems, causing altered brainwave activity, decreased volume of the hippocampus, and abnormal activation of the amygdala. Both the hippocampus and the amygdala are involved in the processing and integration of memory. The amygdala has also been found to be involved in coordinating the body’s fear response.

Psychophysiological alterations associated with PTSD include hyperarousal of the sympathetic nervous system, increased sensitivity of the startle reflex, and sleep abnormalities.