Many agree that yawning is a reflexive deep inhalation caused by decreased oxygen levels in the blood, and is most often associated with sleepiness or boredom. Excessive yawning (1-4 yawns per minute) is associated with a variety of conditions.
There are two things that happen when we yawn, those being that we open our jaw wide and we take a very deep breath. This only happens for a moment and creates a tremendous pressure in the lungs. Although some scientists offer the low oxygen hypothesis, others believe yawning may be:
These possibilities overlap in large part, but none appear to have been unequivocally proven. Whatever the physiology behind yawning, it is clear that it is a basic motor behavior; yawning can remain intact in an otherwise paralyzed person, and yawning has been reported in fetuses.
The majority of disorders associated with yawning are those of the central nervous system, including epilepsy, encephalitis, brain tumors, multiple sclerosis and progressive supranuclear palsy. Excessive yawning is also associated with opiate withdrawal and the consumption of a variety of drugs that affect neurotransmitters, such as drugs prescribed for Parkinson's disease or depression. Studies have shown that people with brain lesions, tumors and certain kinds of epilepsy often yawn excessively, while schizophrenics yawn very little.
Yawning can also be the first sign of what is called the vasovagal reaction. Potentially adversive stimuli, such as needle pricks or even generalized anxiety about some future event, can lead to increased activity in the vagus nerve. In some people the increased activity can cause their blood pressure and heart rate to fall. If the reaction is mild, these people may yawn, or feel apprehensive or restless. In more severe cases a person can exhibit dizziness, nausea, palpitation or even fall into unconsciousness.
If the symptom concerns you, you should consult your doctor.
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