A yawn causes the jaw to stretch out, increasing blood flow in the face and neck. The large inhale and rapid heartbeat caused by the yawn also causes blood and spinal fluid to cycle through the body faster. This whole process may be a way to cool down a brain that has gotten too hot.

Excessive yawning complications include: Bleeding—You might experience bleeding around your heart. Sleep disorders—Sleep apnea or insomnia might be a hidden precursor of constant yawning. Heart attack—Heart attacks can occur with severe yawning.

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.