Yawning is a reflex action that leads to deep inhalation through the mouth followed by short exhalation. It is an involuntary process like the cough reflex and swallowing reflex. While yawning is a normal mechanism, the exact cause of it is still not yet fully understood. However, in cases where it is excessive, yawning has been linked to certain diseases.
What causes yawning?
The exact cause of a yawn is not well understood. It appears to occur more frequently when a person is tired, sleepy and/or bored. Yawning is also associated with reduced oxygen levels in the blood although it also occurs in hyperventilation. It also believed to be a means of arousing a person who is on the verge of falling asleep or who is severely fatigued.
Another theory is that yawning may be a means of conveying one’s fatigue or boredom in a social setting. The ‘contagious yawn‘ may be the result of one person watching another yawn which inadvertently triggers the same reaction. However, this could also be as a result of boredom among both parties. It has also been hypothesized that yawning may be a thermoregulatory mechanism that serves to cool the brain due to elevated temperatures.
It is unlikely that one reason can solely explain the cause or significance of yawning, and the yawn reflex may serve multiple functions. Whatever the reason, yawning is a complex brain stem reflex that may signal serious disease when it is frequent and excessive.
Causes of Excessive Yawning
Physiological causes are not related to any disease process.
- Insufficient sleep
- Shift work (night-shift, day-shift)
- Jet lag
Excessive yawning may be a symptom of many disorders (pathological causes).
- Excessive daytime sleepiness
- Sleep apnea
- Hyperventilation syndrome
- Anxiety disorder
- Brain tumor
- Human African trypanosomiasis (sleeping sickness)
- Vasovagal reaction – may precede nausea, dizziness, fainting
- Heart attack
- Aortic dissection
- Withdrawal from sedatives or opiates
- Carbon monoxide poisoning