We yawn when tired as a sign of drowsiness, and yawning may help cool the brain and increase alertness.
Common reasons
- Drowsiness and low alertness.
- Boredom.
- Brain cooling: studies suggest yawns help regulate brain temperature.
Facts
A yawn lasts about 6 seconds. Yawning is contagious.
Other causes
Sleep disorders, medicines and conditions like multiple sclerosis (rarely).
See a doctor
If yawning is excessive and not linked to tiredness.
Yawn facts
A yawn lasts about 6 seconds on average. Humans begin yawning in the womb at around 11 weeks of gestation. Most mammals, birds and reptiles also yawn.
Brain cooling theory
Research by Andrew Gallup suggests that yawning helps cool the brain by increasing blood flow and drawing in cooler air. Studies found people yawn less when it is very hot or very cold and more at moderate temperatures.
Arousal and alertness
Yawning occurs before and after sleep and when bored, and it may temporarily increase alertness by stretching muscles and raising heart rate.
Contagious yawning
Seeing, hearing or reading about a yawn can trigger one. Contagious yawning starts around age 4 or 5 and is linked to empathy and social bonding. It appears in dogs and chimpanzees too.
Old oxygen theory
The idea that yawning increases oxygen or removes carbon dioxide was tested in 1987, and breathing extra oxygen or carbon dioxide did not change yawning.
Medical causes
- Sleep disorders such as sleep apnea, insomnia and narcolepsy.
- Medications, including some antidepressants (SSRIs) and opioids.
- Heart problems or vasovagal responses in rare cases.
- Neurological conditions such as multiple sclerosis or epilepsy.
Frequent yawning
Yawning that happens excessively, many times in an hour, or comes with other symptoms like chest pain, dizziness or tiredness during the day should be discussed with a doctor.
Tips
Get 7 to 9 hours of sleep, take movement breaks, drink water and get fresh air.
Brain cooling and contagious yawning
A yawn lasts about 6 seconds on average and draws in cool air. Research by Andrew and Gordon Gallup suggested that yawning helps cool the brain, since yawning frequency rises when the surrounding temperature is near body temperature and falls in very hot weather. Yawning is also linked to changes in arousal, appearing before sleep and on waking. The older theory that yawning increases oxygen has not been supported by experiments. Contagious yawning, seen when someone else yawns, begins around age 4 or 5 and occurs in roughly 40 to 60 percent of adults, with links to social connection that scientists still debate.
Frequent yawning and sleep
Excessive yawning can come from lack of sleep, boredom, medications such as some antidepressants and opioids, and sleep disorders including sleep apnea and narcolepsy. Rarely, it can be a sign of vasovagal reactions or neurological problems. Adults need 7 or more hours of sleep, according to the American Academy of Sleep Medicine. Keep a regular schedule, get daylight, limit caffeine late in the day and take short walks to feel alert. See a doctor if yawning is constant, even after enough rest, or comes with daytime sleepiness that affects driving or work.
Based on data from the American Academy of Sleep Medicine and the journal Physiology and Behavior
