Yawning involves opening the mouth involuntarily while taking a long, deep breath of air. This is usually done as a result of drowsiness or weariness. Excessive yawning is yawning that happens more often than expected, even if drowsiness or weariness is present.
Drowsiness or weariness
Disorders associated with excessive daytime sleepiness
LeWinter MM, Tischler MD. Pericardial diseases. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 75.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.