Volume CXXXII, Number 9 November 15, 2002 f

What is all the yawning about?
JEFF BENSON, M.D.

Dear Dr. Jeff: "Is yawning really contagious?" S.F.

Michael Chan getting a little oxygen. (Kid Wongsrichanalai, Bowdoin Orient)

Dear S.F.: It does sometimes seem that yawning is very contagious! To try to answer your question in greater depth, though, I'd like to consider, physiologically speaking, what yawning is really about.

It's thought that yawns are brought on by dropping levels of oxygen in our blood, and triggered by sudden rises in the level of carbon dioxide. They're our bodies' way of quickly "gulping down" that needed oxygen.

Yawning is an involuntary sign of fatigue, of course, but clinically can also be a symptom of other, more complex conditions. Yawning can signal hypoglycemia, or low blood sugar. It's a well-known sign of opiate withdrawal. Frequent yawning can be a side effect of the SSRI anti-depressants, like Prozac or Paxil. "Crescendo yawning" can signal incipient vaso-vagal syncope, or fainting. And excessive yawning and sighing are common features of depression and grief reactions.

Now, back to the contagion question. I tried quite diligently to research this issue, but came across very little useful data or insight. "Goaskalice" did have three theories to offer. Physiologically speaking, if yawning is a reflex triggered by our bodies' need for increased oxygen, then maybe, in a setting where you are not getting enough oxygen (e.g. a stuffy lecture hall), others are lacking it as well. Seeing someone else yawn may somehow remind you that your own body is deprived of oxygen, provoking your yawn, in much the same way that watching someone eat can make your own empty stomach growl with hunger.

Behaviorally speaking, yawning may simply be a way of displaying to others that you are bored or tired (back to that lecture hall). By yawning back, they are "agreeing" that they feel the same way.

Evolutionarily speaking, yawning may be an atavistic, vestigial behavior, left over from our cave-dwelling days, when it served as some sort of social signal within our packs, perhaps like the teeth-baring expressions of dominance or intimidation still favored by other members of the animal kingdom.

The fairest answer to your question is: I don't know! Your guess is as good as mine or Alice's! And if you have any ideas, please let me know.
To your health!

Jeff Benson, M.D.
Dudley Coe Health Center