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mise à jour du
25 mai 2008
Drug-induced yawning: A vital protective reflex
Hari Prasad
Medical Research Faculty, Microbiology,
K.S. Hegde Medical Academy, Deralakatte, Nithyanandanagar P.O., Mangalore, Karnataka, India
 
Amelioration of pathological yawning after tracheostomy in a patient with locked-in syndrome: a thermo-regulatory approach H Prasad 2008

Chat-logomini

Yawning is a complex stereotyped reflex, the physiological function of which remains unknown. Yawning can be drug-induced, and antidepressants, in particular serotonin reuptake inhibitors, are drugs that have been implicated in excessive yawning [1]. However, the reason why drug-induced yawns occur is a bit of a mystery. There is also very little research, because for most people yawning is not a problem. It would be therefore interesting to explore whether excessive yawning among patients is an unwanted, negative consequence associated with the use of antidepressant medications or has an important beneficial role in regulation of brain homeostasis.
 
Recently, an interesting article in Medical Hypotheses has identified that majority of therapeutic strategies against mania are hypothermic, while thermogenic strategies are used to combat depressive disorders. Hence, during treatment, brain temperature may rise in patients with depression, and fall in patients with mania [2]. Studies have revealed that yawning has many physiological consequences that are concordant with those needed for the regulation of brain temperature [3]. I therefore propose that the drug induced yawning serves as a compensatory brain cooling mechanism when regulatory mechanisms fail to operate favourably. Another interesting aspect is the inhibitory role of opioid system on yawning [1], which could be possibly explained on the basis of their hypothermic action (antimanic property) [4].
 
In general, therefore, whenever there is an increase in brain temperature, protective mechanisms such as the one described here, are triggered. Failure of the latter will lead to an increase in the severity of adverse effects with life-threatening consequences. I believe that the human yawn reflex is a vital protective reflex, and its integrity is important to keep the brain in thermal homeostasis. I suggest that excessive yawning should be viewed as an important warning sign of CNS toxicity, but not as the ''side-effect'' of drug usage. More clinical and basic research in this area is needed to advance our understanding of the pathogenesis of drug-induced yawning.
 
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References
  1. Sommet A, Desplas M, Lapeyre-Mestre M, Montastruc JL. Drug-induced yawning: a review of the French pharmacovigilance database. Drug Saf 2007;30(4):327&endash;31.
  2. Salerian AJ, Saleri NG, Salerian JA. Brain temperature may influence mood: a hypothesis. Med Hypotheses 2008; 70(3):497&endash;500.
  3. Gallup AC, Gallup Jr GG. Yawning as a brain cooling mechanism: nasal breathing and forehead cooling diminish the incidence of contagious yawning. Evol Psychol 2007;5(1):92&endash;101.
  4. Sandyk R. Antimanic effects of clonidine and the endogenous opioid system. Am J Psychiatry 1985;142(8):992&endash;3.
mise à jour du
25 mai 2008
Yawning.. and why yawns are contagious:
a theory on evolution and atavism
Hari Prasad
Chat-logomini
I would like to congratulate Matikainen and Elo on their unearthing of mechanism giving rise to increased arousal, alertness and wakefulness, while yawning [1]. Observational studies on animal and human yawning yield important clues for understanding primate evolution. In response to this article, I would like to draw your attention to our observation regarding contagious yawn usage in humans, which I believe may help enhance our knowledge of human and primate evolution.
 
We have all noticed that when one person yawns, it sets off a chain reaction of yawns amongst others in the group. However, the reason why yawns are contagious is a bit of a mystery. There is also very little research done, because for most people contagious yawning is not a problem. It was previously thought that, while yawning occurs in many animal species, only humans yawned contagiously. It turns out, chimps and stumptail macaques may yawn contagiously as well [2,3]. Its universal and widespread nature suggests that it must have either functional or atavistic basis, if not so [4].
 
In non-human animals, contagious yawning can serve as a warning signal. For example, baboons use yawn to threaten their enemies, possibly by displaying large, canine teeth [5]. Although human beings no longer require the use of displaying their unimpressive incisor teeth to exhibit dominance or anger, It is possible that a contagious yawn is a vestigial reflex, similar to the formation of goose bumps in humans under stress, because at one time in evolutionary history, the yawn served to coordinate the aggressive social behaviour of a group of animals. I strongly believe that this unconscious automatic action is a non-anatomical, physiological atavistic trait present in humans.
 
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References
  1. Matikainen J, Elo H. Does yawning increase arousal through mechanical stimulation of the carotid body. Med Hypotheses 2008;70(3):488&endash;92.
  2. Anderson JR, Myowa-Yamakoshi M, Matsuzawa T. Contagious yawning in chimpanzees. Proc Biol Sci 2004;271(Suppl. 6): S468&endash;70.
  3. Paukner A, Anderson JR. Video-induced yawning in stumptail macaques (Macaca arctoides). Biol Lett 2006;2(1):36&endash;8. [4]
  4. Kumar A, Kumar CJ. Atavistic orofacial response to manually dextrous activities. Med Hypotheses 2005;65(1):196.
  5. Darwin CR. Special expressions of animals. In the expression of the emotions in man and animals. 1st ed. London: John Murray; 1872. p. 116&endash;46.