Why do we yawn — and why is it so contagious? Experts explain.

Your body has millions of parts working together every second of every day. In this series, Dr. Jen Caudle, a board-certified family medicine physician and an associate professor at Rowan University School of Osteopathic Medicine, explains how the body works — and all of its quirks.

Merely thinking about or seeing someone yawn can make you yawn (you’re probably yawning right now). Most people yawn because they’re tired, but it can also happen unexpectedly and without any triggers. While yawning is typically harmless and only lasts about five to 10 seconds, when it occurs excessively it can actually be a symptom of a serious condition.

So why exactly do we yawn? And why is it nearly impossible to stifle a yawn when someone does it in front of you? Let’s find out.

Why do we yawn?

“Most of us equate yawning with being tired, but studies have found that yawning could be caused by your body trying to cool your brain,” Dr. Jen Caudle tells Yahoo Life.

She describes yawning as the body “running the air conditioning in your head.” Here’s how it happens: “Yawning stretches your jaw, increasing blood flow in your neck, face and head. Then a deep breath sends a rush of cool air to the spinal fluid and the brain.”

Caudle explains that we may yawn when we’re tired or sleep-deprived, as these states can increase the brain's temperature.

According to experts, yawning can also happen when you’re hungry, bored, mildly stressed, feeling relaxed or satisfied after a meal.

Is yawning actually contagious?

Yawning is not necessarily “contagious” in the medical sense of the word, Dr. Kecia Gaither, a double board-certified physician in ob-gyn and maternal fetal medicine at the NYC Health and Hospitals System, tells Yahoo Life. But as everyone knows, it’s hard to suppress a yawn when someone is doing it in front of you.

Experts have different theories as to why yawning triggers the same behavior in others. Dr. Hana Patel, a London-based general practitioner in sleep and mental health, tells Yahoo Life that although experts aren’t exactly sure why contagious yawning happens, we tend to copy people when we see them yawning.

Caudle points out that humans, other primates and dogs all find yawning contagious. “It is a common form of echo phenomena — the automatic imitation of another's words or actions, which is basically how we learn,” she explains.

Gaither agrees, saying that this mirroring — unconscious mimicking of a person’s actions — is one theory that helps explain why yawning can seem contagious.

Interestingly, a 2018 study linked yawning to empathy. It suggests that people who yawn after seeing others yawn are likely to be highly empathetic.

Can yawning be a sign of a health problem?

In some cases, yes, says Patel. She warns that frequent yawning may be a sign of sleep problems, such as “sleep deprivation, insomnia, sleep apnea, narcolepsy or a side effect of medicines that cause sleepiness.”

People experiencing coffee withdrawal may also yawn repeatedly for several days. Yawning is considered excessive when it happens three or more times in 15 minutes and with no obvious triggers. It can be a symptom of stroke, bleeding around the heart, brain tumors and migraine.

If you’re concerned about the frequency of your yawning, Patel recommends that you see your health care provider for an evaluation.

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