Sighing is a pattern of breathing known to occur during negative emotions like stress as well as during positive emotions like relief, so these emotions are the most obvious answers when the question “Why do people sigh?” is asked. A person sighs by taking a deep, audible breath, which increases the amount of air entering his or her lungs.
Sighing can be done through the nose with the mouth closed. Alternatively, you can sigh with your mouth only partly open rather than widely open like when you yawn.
Babies are often observed sighing in their sleep. An adult may sometimes sigh after a long period of low-volume tidal breathing. Tidal air is a medical term used for the air that passes in and out of the lungs in an ordinary breath. For a normal adult male, five hundred cubic centimeters of air is an average tidal volume.
Some researchers who study breathing patterns believe they found their answer to “Why do people sigh?” when they recorded the breathing of eight men and thirty-four women. In their results, the subjects’ respiratory dynamics were different before and after a sigh.
The researchers’ hypothesis was that sighing functions like a reset button of the human respiratory system. Their hypothesis is based on the concept of breathing as an intrinsically dynamic and somewhat disorderly physiological system that needs an occasional disturbance factor, which can be provided by a sigh.
During times of stress, breathing is less variable. Letting out a sigh can reset the respiratory system and loosen the alveoli (or air sacs) in the lungs. A sensation of relief can accompany this reset. Some will not even ask “Why do people sigh?” since they already think sighing a few times can help distressed people feel better.
A clinical psychologist who extensively studied the role of breathing in psychological disorders cautioned that too much sighing might not help one’s system. For a person going through a panic attack, for example, sighing would probably not be effective. Panic victims’ hyperventilation would prevent sighing from being useful for them. A sigh is considered a coping mechanism when a person has to deal with an unpleasant thought.
Another way that scientists approach the topic of “Why do people sigh?” is to study the contexts in which this expression tends to happen. The researchers used noise to induce stress in the subjects then induced relief by ending the stressor or by allowing them to anticipate that no stressor would be introduced. Results from this research consistently indicated that people had a higher rate of sighing during the conditions of relief compared to the conditions of stress.