- Andrew
C. Gallup. Yawning and the thermoregulatory
hypothesis
-
- Recently, Chen and Lu (2009) describe how
the use of venlafaxine as treatment for major
depressive disorder produced a disturbing and
disabling instance of excessive yawning. They
found that this side effect was dose-dependent
and was relieved by decreasing the dose, yet
they fail to identify a mechanism that may
mediate this response. The purpose of this
letter is to call attention to a strong
connection between yawning and
thermoregulation.
-
- We believe this view of yawning may provide
critical insight into the understanding and
treatment of this and similar cases in the
future. There is growing evidence that yawning
is a thermoregulatory mechanism and that the
physiological actions following a yawn function
to promote cerebral cooling (Gallup and Gallup,
2007, 2008). Well documented brain cooling
mechanisms (i.e., nasal breathing and forehead
cooling) diminish the incidence of yawning in
human subjects (Gallup and Gallup, 2007), and
rising ambient temperature has been shown to
increase yawning (Gallup et al., 2009).
-
- In addition, a growing body of medical and
physiological evidence shows that yawning occurs
before, after, and during instances of abnormal
thermoregulation, heat stress, and hyperthermia
(Gallup and Gallup, 2008). For instance,
conditions such as central nervous system
damage, epilepsy, migraine headaches, multiple
sclerosis, sleep deprivation, and stress and
anxiety have all been linked to thermoregulatory
dysfunction and am often associated with an
increased yawn frequency.
-
- Similarly, drugs that increase brain
temperature have been shown to produce excessive
yawning, while drugs which produce hypothermia
inhibit yawning (Gallup and Gallup, 2008;
Prasad, 2008a). Serotonin is a vasoactive
compound that regulates skin blood flow, and
therefore is intrinsically involved in
thermoregulation (Maurer Spurej, 2005).
Increases in serotonin are linked to increases
in brain and core temperatures (Myers, 1981;
Schwartz et al., 1995), and night s sweats have
also been reported by women taking selective
serotonin reuptake inhibitors for treatment of
depression (Shahine and Lathi, 2006).
-
- Chen and Lu (2009) have shown that another
common and well documented side-effect of
selective serotonin reuptake inhibitors used for
antidepressant therapy is excessive yawning.
Overdose of o venlafaxine by itself has been
linked to thermoregulatory dysfunction;
producing seizures in two independent cases
(Durback and Scharman, 1997; Leaf, 1998), while
inducing serotonil) syndrome in another
(Kolecki, 1997).
-
- Moreover, two separate case reports describe
the use of benztropine to counter the effects of
venlafaxine-induced sweating (Garber and
Gregory, 1997; Pierre and Guze, 2000).
Therefore, it s would appear that excessive
yawning may be a consequence of increases in
brain and core temperature produced by such
drugs (Gallup and Gallup, 2008; Prasad, 2008a).
Excessive yawning has been shown to reduce
overall body temo perature.
-
- In a report of two women suffering from
abnormal thermoregulation accompanied by chronic
and debilitating bouts of excessive yawning, one
took her underarm temperature prior to and
following a series of excessive yawning episodes
over a period of days, and found that in 9 out
of 10 instances her temperature went down by an
average of .36 C on each occasion (Gallup and
Gallup under review). This is consistent with
the view that yawning contains a cooling
component and that similar to other cooling
mechanisms, yawning may be triggered by
increases in brain and/or body temperature. We
agree with Chen and Lii (2009) that excessive
yawning should not be trivialized when indicated
as a side effect to various conditions or drugs;
however we argue these symptoms may be a
diagnostic indicator of thermoregulatory
dysfunction.
-
- -Nayak R,
Bhogale GS, Patil NM. Venlafaxine and
excessive yawning: is there any link? J
Neuropsychiatry Clin Neurosci. 2011
Spring;23(2):E56-7.
-
- -Philibert
C, Sauveplane K, Pinzani-Harter V et al. Le
bâillement: de la physiologie à la
iatrogénie. La lettre du pneumologue.
2011;14(5):168-172
-
- References
-
- Chen CH, Lu
ML Venlafaxine-induced excessive yawning.
Prog Neuropsychopharmacol I Biol Psychiatry
2009:33:156-7.
-
- Durback LF, Scharman EJ. Seizure resulting
from venlafaxine overdose. Ann Pharmacother
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- Gallup AC,
Gallup Jr GG. Yawning as a brain cooling
mechanism: nasal breathing and forehead cooling
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- Gallup Ac,
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- Garber A, Gregory RJ. Benztropine in the
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- Kolecki P. Isolated venlafaxine-induced
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- Prasad H.
Drug-induced yawning: a vital protective reflex.
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- Prasad H.
Amelioration of pathological yawning after
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- Shahine LX, Lathi RB. Night sweats and
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C. Gallup. Yawning and the thermoregulatory
hypothesis
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