According to Osho, yawning is a mechanical reflex that occurs as sleep approaches: breathing slows, carbon dioxide builds up, and—when we resist sleeping—the body expels this CO2 with a sudden wide-mouthed breath, drawing in fresh oxygen. Yawning thus momentarily counteracts drowsiness and resets the gas balance, signaling that rest is needed and helping maintain wakefulness if we insist on staying up.
When you’re sleepy but keep yourself awake, a yawn dumps extra CO2 and pulls in oxygen to give you a brief wake-up signal.
From the Discourses
Passages where Osho speaks to this question — each links to the complete discourse.
Osho, what use does yawning have for the body? Is it merely a tamasic bodily process? Or is it always an indication of the mind’s boredom?
Sleep is coming, but you are watching a film. The body is ready for sleep—the body has nothing to do with the film. Carbon dioxide has accumulated and you are forcing yourself to stay awake. Then the carbon dioxide is expelled with a jolt—that is the yawn. That is why you open the mouth wide; through that wide opening the accumulated carbon dioxide is thrown out and oxygen rushes in. It is the body’s emergency, crisis action, because there is so much carbon dioxide while you are trying to remain awake. You are sitting in a religious gathering, or singing hymns, or meditating, but the body wants to sleep. Whenever you go against the body—when the body is preparing to sleep and you do not go—what is the body to do? It has accumulated carbon dioxide; it will throw it out. Throwing out the carbon dioxide produces yawning. Such yawning…
Questioner: you said that the ratio of oxygen and carbon dioxide changes through deep breathing. Will you please explain how this matter is connected with the awakening of the kundalini?
There are many connections between them. One, we carry within us the potential for both life and death. While the oxygen of breath represents our potential for life, carbon dioxide represents the potential for death. When your oxygen gradually diminishes and disappears and you are left with carbon dioxide alone, you will turn into a corpse. It is like we burn a piece of wood--it keeps burning so long as oxygen is available. There is fire, there is life in the wood so long as oxygen is available to it. But as soon as its oxygen is spent, it is dead. It is reduced to ashes, to coal, which is carbon. The carbon which is left behind is nothing but dead fire. Both the elements are operating within us. If we have more of carbon dioxide, we will slide into lethargy. That is why it is easier to sleep in…
Osho, you once said that taking deep breaths changes the ratio of oxygen and carbon dioxide. How is this shift related to the awakening of kundalini?
So on the one hand he is attending to the breath twenty-four hours, and on the other he is being given medicines. A great problem arose for him, because a conflict was created in his body. The medicines were trying to make him sleep, and the deep-breath experiment he was continuing around the clock was awakening his energies. It was as if someone were pressing the accelerator and the brake of a car at the same time—you understand, don’t you? He was in great trouble. Someone told him about me, so he came. Seeing him I understood he had fallen into a kind of madness—this simply cannot be. I told him, stop Anapanasati. He said, what has that to do with it? He had no idea that if you do so much breath-work that oxygen becomes so abundant that the body simply cannot sleep, then how will you sleep! Or…
The high energy people move fast in speed. They jump. They leap. With them, work is very fast. That's good, but there is one problem with them: whatsoever they achieve, they can lose as easily as they achieved it. They fall back very easily because it has been jumping, not a growth. Growth needs very slow ripening, seasoning, time. Both types have their benefits and weaknesses and in fact if one has to choose between the two, the low energy people are more capable of spiritual growth than high energy people. High energy people are more powerful as far as worldly achievement is concerned. Low energy people will be defeated in a worldly competition. They will always lag behind. That's why they have become condemned. There is such competition in the world. They will fall out of the rat-race; they will not be able to remain in it.
Saliva? Yes, saliva; it isn’t available down by the stomach, and in its absence the stomach has to do extra labor. And it is true that when an organ does its own work it becomes strong. But if it is made to do work that isn’t its own, it gets depleted—because it is carrying an extra burden.
And here is an even more curious point: when we divide much of the stomach’s work—some done by the mouth, some by the stomach—our energy cannot remain concentrated in the stomach; it begins to be freed from it. That is why as soon as you eat, drowsiness sets in: the stomach summons the power that was in your brain into itself. It says, “Now put that to work too; food is fundamental to life. Thinking and so on are secondary; we will attend to them later—first let the stomach digest.” So the moment you eat, the mind wants to sleep. The reason is that the energy has been called back from the brain. The more work the stomach has, the weaker the brain becomes, because the stomach will need that much more energy, and it will draw it from the non‑essential parts of life. The brain is a luxurious organ;…