Although worry hijacks aspects of our emotional circuitry, chronic worriers seek to control their emotions—and their fretting does tend to numb emotional responses. For instance, it is fairly well established that damage to the frontal lobe—which, as the Boston University study showed, has been demonstrated to be more active in worriers who are thinking about the future—is associated with blunted, or an absence of, emotions. In another emotion-damping mechanism, several studies have confirmed that excess fretting reduces activity in the sympathetic nervous system in response to a threat. This branch of the nervous system normally allows the body to react quickly to impending danger by accelerating breathing and also increasing heart rate to oxygenate muscles to fight or flee.
In one classic study from 1990 Borkovec showed by observing heart rates how worry can dull emotional reactions. He found that people with anxiety about public speaking did not experience variations in their heart rate when relaxing, remaining neutral (that is, neither worrying nor relaxing) or engaging in worry before viewing scary images. After seeing the images, however, subjects in the worry group displayed significantly less variation in heart rate than those in the neutral or relaxed condition, despite reporting feeling more fearful.
At the same time, worry hinders a person’s physical reaction to a threat by amplifying activity in the parasympathetic nervous system. When working properly, this part of the nervous system quiets the body as it recovers from a stressful experience. I experienced this system in operation when I participated in a study in Mennin’s laboratory at Yale. The scene was a lone arm suspended in midair. A hand carrying a razor started slicing it. Blood seeped out of the wound as the razor dug deeper, exposing a mass of blood and cartilage. I wanted nothing more than to look away. Amelia Aldao, the Ph.D. student conducting the experiment, wanted to measure my physiological reaction to various film segments, each one meant to elicit a distinct emotion (for instance, disgust in the case of the mutilated arm).
Aldao recorded with electrocardiography how I dealt with a variety of emotions (this Yale study was the first to expand beyond fear), removed the electrodes from my body and led me into the adjacent room. She did some quick calculations on her computer and out popped a few of my stats. Good news. My heart rate variability was high, and my average heart rate measured about 58 beats per minute. These values indicated that my heart could cope well with intense emotions.
In contrast, by consciously trying to be ready for the worst, worriers are actually compromising their body’s ability to react to a truly traumatic event. In 2006 researchers at Columbia University, the National Institute on Aging and Leiden University in the Netherlands reviewed more than two dozen studies and found that overworrying can tax the body and promote cardiovascular problems. Overall, increased worry was associated with an elevated resting heart rate but low heart rate variability Excessive worriers and GAD patients experienced lower heart rate variability during periods of worry; in other words, their hearts returned to a resting rate more slowly than those of healthy worriers did. Prolonged periods of stress even weakened participants’ endocrine and immune function. Some studies reported that excess worry is linked to elevated levels of the stress hormone cortisol, which slows immune responses and may make chronic worriers more susceptible to disease.
Source of Information : Scientific American Mind November-December 2009