Why Do We Yawn?

Medically Reviewed by Jabeen Begum, MD on March 15, 2024
Written by Frances Gatta, WebMD Editorial Contributor, Amy Gopal
7 min read

Yawning is a common reflex in which you open your jaw wide, take a deep breath, and then quickly breathe out. It lasts about 4-7 seconds and often happens when you're waking up or falling asleep.

Yawning begins in the womb as early as the 11th week of pregnancy and continues for a lifetime. When you yawn, a wetting agent known as a surfactant coats the tiny air sacs (alveoli) in your lungs, which helps keep them open.

Although no one knows exactly why we yawn, new studies suggest that yawning may not always be a sign you’re tired or bored, as most people believe.

Interestingly, many people feel more relaxed after yawning.

Why do we yawn?

Yawning may be contagious or spontaneous. Contagious yawning happens when you see, hear, feel, or think about someone yawning. On the other hand, spontaneous yawning occurs without any obvious trigger.

According to a popular theory, a yawn can help cool the brain when it’s warming up. Researchers think this cooling happens for two reasons:

  • Yawning opens up the muscles in your skull and jaw to increase blood flow to the brain
  • Yawning causes you to breathe in deeply, which increases blood flow in the veins in your brain and allows cooler air in.

Some other studies suggest that yawning might do more than cool the brain.

Researchers think when you yawn, you may be communicating how you feel, whether you’re tired, bored, or under mild stress. Some researchers also think that yawning is an empathetic and social skill where we show that we connect with others.

Why is yawning contagious?

Contagious yawning starts in early childhood. You might yawn after seeing, hearing, or thinking about someone else yawn. In fact, seeing your pet or animals such as fish, birds, and apes yawn may also make you yawn.

Contagious yawning is believed to have evolved as a way to stay alert and in sync in a group. It may also be a way of telling other people that you feel the same way (maybe bored) about a situation or experience.

Research suggests that contagious yawning may be linked to empathy, which is feeling and understanding someone else’s experience, and people who yawn after seeing others yawn show higher empathy. You’re also likely to yawn when someone you’re close to or care for yawns.

There's no specific reason why you yawn. Regular yawning is a reflex in your body that happens involuntarily, meaning you do it without thinking about it. However, there are many things that researchers agree cause yawning.

Change in elevation

If you’re in an airplane or driving at different elevations, you might yawn on purpose or as an automatic response from your body. It can help equalize the pressure in your ears.

Empathy 

Another cause of yawning is social empathy. You might want to yawn if you see someone yawn or even read about yawning. Psychologists say that you’re more likely to yawn when you see someone else do it if you’re more empathetic. Also, the closer you are to someone, the more likely you’ll yawn if they do.‌

Feeling bored or tired

You might yawn when you’re tired or bored. It’s your brain’s way of waking you up or making you feel more alert.‌

Cooling your brain

Another popular explanation is that yawning is your body’s way of cooling your warm brain. The theory is that you will yawn more in situations where you’re overheated. Deep breaths and open mouths have been shown to cool the brain a little. However, more research is needed to confirm how true this theory is.‌

Stretching your lungs and lung tissue

When you yawn, it’s sometimes followed by a larger stretch, which flexes your muscles and stretches your joints. You might also have an increased heart rate. You'll also feel more awake as your lungs stretch and your heart rate increases.

Yawning while working out

You might yawn while exercising because your brain needs cooling to stay alert and active for your workout, or perhaps the alveoli (tiny air sacs) in your lungs need more support to stay open. But yawning during exercise isn’t a cause for concern, and you can continue your workouts after yawning.

Yawning and anxiety

You may also yawn when you’re anxious or nervous. But no one knows exactly why this happens. One way to explain it is that when you’re anxious, your body activates the sympathetic nervous system. This system keeps you hyperalert, aware, and ready to take action in response to a threatening situation. At the same time, your body may also activate your parasympathetic nervous system to make you relax, resulting in yawns.

Certain anti-anxiety medications increase your serotonin levels and make your body temperature rise, so yawning can be a side effect.

Yawning is also a symptom of anxiety in animals such as dogs.

Constant yawning and shortness of breath

Constant yawning and issues with your breathing may be symptoms of health problems like anxiety, panic attacks, or heart, lung, and breathing problems. Sometimes, these symptoms may occur without any apparent reason and may not be a cause for alarm, as you can manage them by doing breathing exercises. But it’s best to see a doctor if you’re yawning and short of breath without any obvious reason, such as working out.

When you start to yawn a lot and you can't stop, you might begin to worry. Excessive yawning may be caused by sleep deprivation from any of the following conditions:

  • The day after a late night out
  • Stress resulting in sleep disturbance
  • Insomnia, a condition where you have trouble falling asleep or staying asleep
  • Sleep apnea, a condition that interrupts your breathing when you sleep
  • Narcolepsy, a condition that makes you extremely sleepy during the day

Taking medication that makes you very tired may also cause excessive yawning. Or it may be a symptom of an underlying condition. Sometimes, it can also be a symptom of a serious medical problem, such as:‌

If you're doing something repetitive or uninteresting, you might not be able to stop yawning. Tasks such as watching television, listening to a lecture, studying, or driving can put you in a low-active state that makes you yawn more.‌

Thermoregulatory disorders and intense headaches can also cause excessive yawning. Researchers believe a circulatory dysfunction may cause this.

Not being able to stop yawning might be your body’s way of showing that your circulatory system isn’t working or that your body can’t regulate its body temperature.

If you start yawning too often and are unsure why, you should talk to your doctor. An underlying medical condition might cause excessive yawning. It’s a good idea to ask your doctor what may be the cause.

Yawning is a common reflex that can happen to anyone at any time. It’s usually not bothersome, except when it happens too frequently in a short time. Consider seeing a doctor if it bothers you how often you yawn or if sleep problems are causing you to yawn often. Also, get immediate medical attention if yawning comes with other symptoms including shortness of breath, chest pain, dizziness, and headache.

Is yawning a sign of stroke?

Yawning may be a sign of stroke. But this is rarely the case, especially if you have no other symptoms such as face, arm, or leg numbness or weakness; trouble speaking, walking, or seeing; dizziness; and headache. If you do experience these symptoms, get emergency medical care right away.

Why do my eyes water when I yawn?

Your eyes may water because yawning causes muscles in your face to tense up and stretch, which might affect your tear glands, causing your eyes to water.

Tiredness can also cause dry eyes, making your eyes water at the same time you're yawning due to feeling sleepy.

Does yawning indicate a lack of oxygen?

Researchers initially thought that yawning might mean you lack oxygen, but more recent evidence suggests this is untrue. Yawning doesn’t mean you lack oxygen or your body is trying to get more oxygen.

Why do I keep yawning when I'm not tired?

It’s normal to yawn even when you’re not tired. You might yawn during a workout because you saw or heard someone around you yawn, or even when you’re anxious, nervous, or bored.

How many yawns per day is normal?

Older research says it’s normal to yawn up to 20 times a day. But the average person yawns about nine times a day.