On High Alert: The Biology of Chronic Hypervigilance
Traumatized individuals sometimes experience persistent symptoms of chronic hypervigilance. That means they’re on high alert, physically and psychologically, even when not in danger. Symptoms can include feelings of anxiety and physiological markers of “hyperarousal” like a high startle response and elevated heart rate.
Symptoms of chronic hypervigilance are typically self-reported. But a new study published in the journal Psychoneuroendocrinology sought to identify objective biological markers of chronic hypervigilance. The study was conducted by doctoral candidate Olena Kleshchova; Jenna K. Rieder, who has since completed her Ph.D., and Professor Mariann R. Weierich (Hunter College, The Graduate Center, CUNY).
Two groups of women, one “trauma-exposed” and one not, participated. They underwent functional magnetic resonance imaging (fMRI) scans, first while at rest, then while viewing a set of images. The images — some pleasant, some unpleasant, some neutral — were chosen to elicit a range of emotions. The women saw the images twice, so that the first time, they were unfamiliar, but the second time, they were familiar. MRIs measured the synchronization of neural activity between the amygdala and other regions of the brain’s “alarm system.”
Trauma-exposed women showed consistently greater connectivity between the left amygdala and another region of the “alarm system,” the ventral anterior cingulate cortex, in response to emotional scenes. In contrast to the control group, trauma-exposed women also showed greater connectivity when they were at rest, and while viewing familiar scenes. This suggests “an exaggerated and persistent neural alerting response as a neural marker of chronic hypervigilance.”
The study also tested whether a stress-related enzyme in saliva, alpha-amylase (AA), might be a biomarker for hypervigilance. On average, both groups had similar baseline AA levels. But trauma-exposed participants with higher AA levels showed greater neural alerting responses both while viewing emotional images and at rest. The authors suggest that elevated baseline AA levels might indicate sustained activation of the stress system, consistent with chronic hypervigilance.
Establishing reliable biomarkers of hypervigilance remains “a promising avenue for future work,” the authors said. Such markers can help identify trauma survivors who are likely to benefit from treatment aimed at reducing chronic hypervigilance and can also be used to measure treatment effectiveness.