[ sigh ]

A human sigh can convey a plethora of important emotions. We sigh when we are frustrated; we sigh when we are worried; we even sigh when we're relieved. A sigh can be an important social signal to inform others about our current mood, and because of this communicative power, sighs play a prominent role in art and culture around the globe.

The evidence for the connection between sighing and our emotions extends beyond simply what we see in our everyday experiences. For instance, scientific studies have found that intense emotional states, such as those associated with feelings of unpleasantness1 or stress2-3, are associated with increased sighing. Researchers have found that directly inducing emotions such as anxiety can actually cause people to sigh more4. Even rats sigh more frequently under anxiety-provoking circumstances5.

Sighs help bring balance

Given that sighing is so strongly related to emotional states in both humans and animals, they may serve a larger purpose than simply communicating our mood. Specifically, some scientists have speculated that sighs might play an important role in regulating our emotional and physical state, particularly as related to the breath. One of the body's primary goals is to maintain what is known as homeostasis – a state of balance in which things such as body temperature and blood-oxygen levels are kept constant6-7. The breath plays a crucial role in maintaining homeostasis by bringing in fresh oxygen and removing waste carbon dioxide, meaning that it's important that the breath follow regular patterns.

Strong emotional states, especially fear and anxiety, can disrupt breathing. This response is completely normal as the body is trying to increase oxygen flow to help deal with potential threats8-9. However, the body must also have ways to return to homeostasis after the threat has passed. This ability is particularly crucial in situations where a person is experiencing prolonged anxiety, such as in the case of anxiety disorders. Without checks and balances, an individual with an anxiety disorder could experience permanently disrupted breathing, which could cause a whole host of problems.

Dr. Elke Vlemincx at the University of Leuven in Belgium and her colleagues have proposed that sighing may serve just such a function10. Research suggests that sighing can help return breathing to healthy patterns under non-emotional circumstances11. Thus, it may be that sighing helps return breathing to normal patterns after experiencing an emotion such as anxiety or fear. The sigh could serve as, what Vlemincx and her colleagues refer to as, a "psychophysiological reset" – helping to return a person to both a psychological and physical baseline. As evidence for this idea, individuals with chronic anxiety12, post-traumatic stress disorder (PTSD)4, and panic disorder13-16 all seem to sigh more frequently than individuals without these disorders. In other words, it could be that these individuals are sighing more as a means of decreasing their psychological and physiological distress.

To test this possibility, Vlemincx and her colleagues examined the effect of sighing on psychological and physical stress when viewing positive and negative pictures. The researchers had two questions of interest:

1. Does spontaneous sighing, as well as spontaneous breath holding, have a different effect on people as compared to instructed deep breaths and breath holding?

2. Does a person's sensitivity to anxiety change how sighing affects them?

In other words, if you are more sensitive to anxiety, is sighing more or less effective at reducing stress?

Participants completed three sets of trials during which they were presented with positive and negative pictures. In the first set of trials, participants were not given any specific instructions about their breath, and the researchers monitored their breathing for spontaneous sighs and spontaneous breath holding. In the next two blocks, participants were instructed to either take a deep breath or to hold their breath for short period of time in conjunction with the pictures, with the explanation that both of these techniques have been used to reduce stress and anxiety. Throughout participants were asked to rate their current level of relief, while the researchers monitored their muscle tension through electrodes placed on the face.

Take a deep breath

In analyzing their results, the researchers found that all participants reported a greater sense of relief after they were instructed to take a deep breath, indicating that controlled, deep breathing could play a role in reducing stress after an anxiety-provoking event. In regard to spontaneous sighs and breath holding, though, the researchers had two intriguing findings. Participants with a high propensity towards anxiety showed a significant decrease in muscle tension after a spontaneous sigh, whereas participants with a low propensity towards anxiety showed a significant decrease in muscle tension after spontaneously holding their breath. However, neither was associated with a greater sense of psychological relief. These results suggest that both spontaneous sighing and breath holding could play a role in resetting bodily tension after a stressful event, but it is unclear how this reduced bodily tension relates to psychological stress.

To be sure, these results are preliminary, leaving many open questions. For instance, why does spontaneous sighing reduce tension in anxiety-sensitive participants while spontaneous breath holding reduce tension in less anxiety-sensitive participants? One possibility is that individuals who are prone to anxiety associate breath holding with fear or panic attacks, thus breath holding for them may not provide the same relief. Further research is necessary to explore this possibility. In addition, given that spontaneous sighing and breath holding reduced physical tension, you might have expected that they would have been associated with decreased psychological tension as well. It may be that the negative pictures used by the researchers were simply not threatening enough for them to have found an effect. In any case, this research implies that the simple sigh might play an important role in regulating bodily function, beyond serving as a social cue communicating one's mood. This finding could have important implications for how we understand the role of breathing in anxiety disorders and may one day lead to a better understanding of how focusing on the breath could reduce symptoms of anxiety.

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Date of original publication:
Updated on: January 10, 2017

Sources

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2. Vlemincx, E., Taelman, J., De Peuter, S., Van Diest, I., & Van Den Bergh, O. (2011). Sigh rate and respiratory variability during mental load and sustained attention. Psychophysiology, 48, 117-120.

3. Vlemincx, E., Van Diest, I., & Van den Bergh, O. (2012). A sigh following sustained attention and mental stress: effects on respiratory variability. Physiology & behavior, 107, 1-6.

4. Blechert, J., Michael, T., Grossman, P., Lajtman, M., & Wilhelm, F. H. (2007). Autonomic and respiratory characteristics of posttraumatic stress disorder and panic disorder. Psychosomatic Medicine, 69, 935-943.

5. Carnevali, L., Sgoifo, A., Trombini, M., Landgraf, R., Neumann, I. D., & Nalivaiko, E. (2013). Different patterns of respiration in rat lines selectively bred for high or low anxiety. PloS one, 8, e64519.

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10. Vlemincx, E., Abelson, J. L., Lehrer, P. M., Davenport, P. W., Van Diest, I., & Van den Bergh, O. (2013). Respiratory variability and sighing: a psychophysiological reset model. Biological psychology, 93, 24-32.

11. Bartlett, D. (1971). Origin and regulation of spontaneous deep breaths. Respiration physiology, 12, 230-238.

12. Tobin, M. J., Chadha, T. S., Jenouri, G., Birch, S. J., Gazeroglu, H. B., & Sackner, M. A. (1983). Breathing patterns: 2. Diseased subjects. Chest, 84, 286-294.

13. Abelson, J. L., Khan, S., Lyubkin, M., & Giardino, N. (2008). Respiratory irregularity and stress hormones in panic disorder: exploring potential linkages. Depression and anxiety, 25, 885-887.

14. Abelson, J. L., Weg, J. G., Nesse, R. M., & Curtis, G. C. (2001). Persistent respiratory irregularity in patients with panic disorder. Biological Psychiatry, 49, 588-595.

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16. Wilhelm, F. H., Trabert, W., & Roth, W. T. (2001). Characteristics of sighing in panic disorder. Biological psychiatry, 49, 606-614.

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