A new study finds that people with chronic anxiety tend to have higher levels of norepinephrine, a hormone released by sympathetic nerve fibers in response to stress. This greater sympathetic nerve activity is particularly strong just before and during a stressful event in people with chronic anxiety.
Over time, this exaggerated response may increase the risk of high blood pressure and heart disease, although the current study did not test these conditions specifically.
Researchers from the University of Iowa observed the responses of two groups of participants after they experienced physiological and mental stressors. The first group of people suffered from chronic anxiety as determined by standardized scales used to measure anxiety and depression. Participants in the second cohort did not have chronic anxiety and were used as a control group.
The researchers placed the volunteers’ hands in an ice-water bath for two minutes to evaluate their responses to physiological stress. After a brief recovery period, the volunteers had to verbally solve simple math problems as fast as they could for four minutes to induce mental stress.
Before the start of each test, the researchers gave the participants a two-minute “warning” countdown.
Meanwhile, the research team inserted a tiny microelectrode into a nerve near the back of the volunteers’ knee to track sympathetic nerve activity throughout the testing period. They monitored the participants’ rate of blood flow and blood pressure in the upper arm and heart rate via a finger cuff during both of the tasks.
Before testing began, blood samples revealed that participants in the chronic anxiety group had higher levels of norepinephrine, a hormone that sympathetic nerve fibers release in response to stress. Norepinephrine causes the blood vessels to contract, which raises blood pressure.
Although the researchers observed increased nerve responses in both groups before and during the ice bath and math activities, the increase “was significantly greater among [the anxiety group] compared with [the control group], suggesting an enhanced sympathetic anticipatory response,” the research team wrote.
Heart rate increased during the two-minute countdown, another sign that the anticipation of impending stress or discomfort triggered physiological changes in the body. However, no significant difference was found between the anxiety and control groups.
“Future studies are warranted to determine whether augmented [sympathetic nerve activity] is associated with deleterious end-organ consequences in persons with anxiety and cardiovascular disease or cardiovascular disease risk factors,” the researchers wrote.
The findings are published in the Journal of Neurophysiology.
Source: American Physiological Society