Certain serious heart problems, including heart attack and a tear in the aorta, the major blood vessel that carries blood from the heart, can cause excessive yawning, according to MedlinePlus. These conditions cause excessive yawning by stimulating the vagus nerve in what is known as a vasovagal reaction. Another serious cardiovascular condition, stroke, can also cause excessive yawning.
Excessive yawning is yawning beyond what one normally expects for a given level of sleepiness or drowsiness, states MedlinePlus. Brain problems, such as epilepsy, multiple sclerosis and tumors, can sometimes cause excessive yawning. Some disorders that cause excessive daytime sleepiness can also cause excessive yawning. Certain medications can cause excessive yawning as an uncommon side effect. Rarely, problems with the body's ability to regulate its temperature can also cause excessive yawning.
Excessive yawning is a symptom of another underlying condition, so there is no direct treatment, according to MedlinePlus. Treating the underlying condition generally resolves the excessive yawning. Excessive yawning merits medical attention, as does yawning that is associated with excessive daytime sleepiness. Possible causes of excessive daytime sleepiness include diabetes, changes in blood sodium levels, narcolepsy, sleep apnea and underactive thyroid. Too much calcium in the blood and chronic pain can also cause excessive daytime sleepiness.