Département de
Psychologie, Université Paris Ouest, 200
Avenue de la République 92000 Nanterre La
Défense. France
Institute of Criminology,
University of Cambridge, Sidgwick Avenue,
Cambridge, CB3 9DA, United Kingdom
Yawning has fascinated researchers and
clinicians for centuries but has been
controversial and illusive in respect of its
origin, mechanism and usefulness as a predictor
of disease. With the advent of brain scanning
techniques and an increased understanding of
metabolism and neural pathways, a better
understanding of the variance of yawning and
possible associated pathways has been achieved.
Knowledge about yawning has reached a level of
sophistication that makes it possible to be a
predictor of underlying neurological disease and
health problems. Although there is still
considerable inconsistency and lack of consensus
amongst researchers, several hypotheses have
emerged that make the topic worthwhile to pursue
with a view to obtaining a potential diagnostic
tool for health problems.
Le bâillement fascine les chercheurs
et les cliniciens depuis des siècles,
mais son origine, ses mécanismes et son
utilité en tant que prédicteur de
maladie restent controversés et
illusoires. L'avènement des techniques
d'imagerie cérébrale et une
meilleure compréhension du
métabolisme et des voies neuronales ont
permis de mieux comprendre les
variétés de bâillements et
les éventuelles voies associées.
Les connaissances sur les bâillements ont
atteint un niveau de sophistication qui permet
de les considérer comme un indicateur de
maladies neurologiques sous-jacentes et de
problèmes de santé. Bien qu'il y
ait encore beaucoup d'incohérence et un
manque de consensus parmi les chercheurs,
plusieurs hypothèses ont
émergé qui rendent le sujet
intéressant à poursuivre en vue
d'obtenir un outil de diagnostic potentiel pour
les problèmes de santé.
-Thompson SBN.
The dawn of the yawn: is yawning a warning?
linking neurological disorders. Medical
Hypotheses 2010;75(6):630-633
-Thompson
SBN. Born to yawn? Cortisol linked to
yawning: A new hypothesis. Medical Hypotheses
2011;77(5):861-862
-Thompson
SB. Is Yawning A Warning, Neurologically?
2011.
-Thompson SB,
Bishop Ph. Born to Yawn? Understanding
Yawning as a Warning of the Rise in Cortisol
Levels: Randomized Trial. I-jmr.
2012;1(2):e4
-Thompson
SB.Yawning, fatigue, and cortisol: Expanding
the Thompson Cortisol Hypothesis. Med
Hypotheses.Med Hypotheses. 2014
Oct;83(4):494-6.
-Thompson
SB. Pathways to yawning: making sense of the
Thompson Cortisol Hypothesis. Medical Research
Archives 2015(3)
-Thompson
SB, Simonsen M. Yawning As a New Potential
Diagnostic Marker for Neurological Diseases.
Journal of Neurology and Neuroscience.
2015;6(3):22
-Thompson SBN,
Coleman A, Williams N. Yawning and cortisol
levels in multiple sclerosis: Potential new
diagnostic tool. Mult Scler Relat Disord.
2018;23:51-55.
-Thompson
SBN, Sava D. Elevation of Cortisol Levels by
Ingesting Liquorice. Clinical Research in
Neurology 2018;1(1):1-4.
-Thompson
SBN. Yawning as a Potential Diagnostic
Indicator for Underlying Neurological Disorders.
Archives of Neurology & Neurological
Disorders 2002;5(1)
Introduction
Over many centuries various reports on
yawning have emerged. As far back as 400 BC, the
famous philosopher Hippocrates claimed that
yawning usually precedes a high body temperature
and, similar to a large quantity of water
achieving boiling point, the accumulated air in
the lungs reaches a crescendo before opening the
mouth to release the air [1]. This
rather intriguing and simplistic view has since
found identity amongst animal researchers who
have declared a thermoregulatory hypothesis of
yawning [2].
Subsequent clinical evidence has found a
link between rises in body temperature and
episodes of yawning in people with incomplete
innervation such as multiple sclerosis
[3,4]. Temperature lowering seems to
occur following excessive yawning probably
because the air is released followed by feedback
that signals the hypothalamus to regulate body
temperature [5].
The Thompson Cortisol Hypothesis
[6,7] has proposed and shown evidence of
the critical role of cortisol released by
stimulation of the hypothalamus [8].
Corticotrophin-releasing hormone (CRH) released
from the hypothalamus stimulates the anterior
pituitary to then release adrenocorticotropic
hormone (ACTH). This hormone acts on the adrenal
cortex to release cortisol. The increase in
blood cortisol levels signals the hypothalamus
to reduce or stop further release of CRH through
the feedback system [9]. Known as the
H-P-A axis, the hypothalamus-pituitary-adrenal
axis is important for protecting the body
against infection and stress because antigens
are also released by the adrenal glands when
they are stimulated by ACTH [10].
2. Fatigue and Yawning
As well as temperature fluctuations being
observed in incompletely innervated individuals,
fatigue has been commonly reported [11].
Particularly in people with immune suppression
[2], fatigue is an important factor in
recovery from symptomatic episodes of relapsing
multiple sclerosis and in coping with activities
of everyday living [9].
People who have suffered an ischaemic brain
stem stroke have been reported in the context of
yawning where the phenomenon parakinesia
brachialis oscitans (PBO) sees an involuntary
upward movement of the paralysed arm during
yawning [12]. This is perhaps the origin
of the curious and enigmatic fictitious
character in Stanley Kubrick's 1964 film Dr
Strange Love who has an arm that is apparently
under involuntary control [13].
3. Contagious Yawning
Contagious yawning, when yawning is
triggered by the yawns of others, is considered
to be a recent phenomenon in terms of human
evolution [14]. Norscia et al.
[14] predicted that pregnant women would
be more likely to contagiously yawn than
nonpregnant, nulliparous women (i.e., who had
not given live birth). The researchers suggested
that yawning in highly social species such as
humans might be utilised for emotional contagion
during evolution as they found that pregnant
women were more likely to be susceptible to
contagious yawning.
The mirror neuron system has also been
postulated as an explanation of contagious
yawning [15]. Empathy may play an
important role in the elicitation of yawning
contagion [16]. Facial mimicry and yawn
contagion seem to share some of the brain areas
during action including the ventromedial
prefrontal cortex, superior temporal sulcus and
the amygdala [17]. Researchers have
increasingly focused on explanations from
neuroanatomy including the use of MRI brain
scanning techniques to reveal links between
anatomical structures and feedback mechanisms
[18]. Such associations have been found
with the motor cortex and hypothalamus
[19,20].
It is interesting to note that human infants
seem not to show contagious yawning [21]
but it is unclear whether they perceive yawning
in the same manner as other emotional
expressions and differently to adults. However,
preschool children aged between 2.5 and 5.5
years do appear to show the effects of
contagious yawning [22].
4. Frequent Yawning as a Diagnostic
Indicator
Repetitive yawning can be another factor of
note when diagnosing underlying neurological
conditions. Premortem yawning has been reported
consistently in association with acute
infections and haemorrhage including the Bubonic
Plague [23,24]. Vasovagal reflex,
intracranial hypertension, hypoglycaemia,
anaemia, and hypoxia have all been associated
with repetitive yawning [25-27].
Probable cause of yawning with shock may be
a decrease of the central nervous system's (CNS)
adenosine triphosphate production causing CNS
tissue hypoxia and leading to an excess of
glutamate within the paraventricular nucleus. In
turn, yawning, hypotension and bradycardia is
activated [28].
The yawning research team at the
Universities of Bournemouth, United Kingdom and
Paris Ouest Nanterre La De_fense, France led by
Professor Dr Simon B N Thompson, have been the
first to describe the 'yawning envelope' which
is an electromyographical profile of the yawn as
it is being elicited [7]. The yawning
envelope is a capture or snap shot of the yawn
episode [6]. The researchers have
observed association with fatigue, the yawn
envelope (and electromyographical changes during
the yawn) and changes in the level of cortisol
[29].
Brown et al. [30] found an increased
excitability of the cells of the primary cortex
in humans which gives support to the suggestion
that there are specific cortisol receptors in
the motor cortex [10,31] and that these
communicate with the hypothalamus providing
essential feedback for the regulation of
cortisol via the H-P-A axis.
Whilst others have shown involvement of the
dorsolateral prefrontal cortex region in
preparing and maintaining the state of alertness
in individuals during phasic alertness tasks
[32], Anglo-French teams have tested
intrinsic and phasic fatigue in paradigms that
demonstrate association with fatigue and changes
in cortisol levels [18]. This helps
towards an explanation of the frequently
observed fatigue in people with immune
suppression such as multiple sclerosis11 where
rises in cortisol levels have been associated
with fatigue and yawning [9].
5. Conclusion
Expansion of the Thompson Cortisol
Hypothesis [11] purports a threshold
level of cortisol and possibly also
cerebrospinal fluid [33], is necessary
for an episode of yawning to occur.
Communication between the motor cortex and
hypothalamus as seen in MRI studies of yawning
[18] suggest that the motor cortex is
implicated in the regulation of cortisol as well
as previously known structures such as those
dedicated to the H-P-A axis.
Combining findings from past work on
ischaemic stroke and PBO and those of intrinsic
and phasic alertness task studies, helps us
better understand the importance of the
functional role of the brain stem in the
regulation of fatigue, stress and yawning. Using
these data may well contribute towards a further
step in developing a consistent diagnosis for
protracted and disruptive immunosuppression
diseases such as multiple sclerosis in the near
future.
4. Gallup GG Jr, Gallup AC. Excessive
yawning and themoregulation: two case histories
of chronic, debilitating bouts
of yawning. Sleep Breath.
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5. Gallup AC, Gallup GG Jr. Yawning as a
brain cooling mechanism: nasal breathing and
forehead cooling diminish the
incidence of contagious yawning. Evol
Psychol. 2007;5(1):92-101.
6. Thompson SBN, Frankham C, Bishop P. The
art of capturing a yawn using the science of
nerve impulses and cortisol
levels in a randomized controlled trial.
Thompson Cortisol Hypothesis as a predictor of
neurological impairment. Int
J Arts Sci. 2014;7(3):529-43.
7. Thompson SBN. Born to yawn? Cortisol
linked to yawning: a new hypothesis. Med Hyp.
2011;77:861-2.
8. Thompson SBN, Bishop P. Born to yawn?
Understanding yawning as a warning of the rise
in cortisol levels:
randomized trial. Interact J Med Res.
2012;1(5):e4:1-9.
9. Thompson SBN, Coleman A, Williams N.
Yawning and cortisol levels in multiple
sclerosis: potential new diagnostic
tool. Multiple Sclerosis Rel Dis.
2018;23:51-5.
10. Thompson SBN. Pathways to yawning:
making sense of the Thompson Cortisol
Hypothesis. Med Res Archiv.
2015;3:1-7
11. Thompson SBN. Yawning, fatigue and
cortisol: expanding the Thompson Cortisol
Hypothesis. Med Hyp.
2014;83(4):494-6.
12. Walusinski O, Neau J-P, Bogousslavsky J.
Hand up! Yawn and raise your arm. Int J Stroke.
2010;5:21-7.
13. Kubrick S. Dr Strangelove, or: how I
learned to stop worrying and love the bomb.
Columbia Pictures Corp; 1964.
14. Norscia I, Agostini L, Moroni A, et al.
Yawning is more contagious in pregnant than
nulliparous women. Hum Nat.
2021;32:301-25.
15. Norscia I, Palagi E. Yawn contagion and
empathy in homo sapiens. PLoS One.
2011;6(12):e28472.
16. Dhar DK, Arora R. The mystery behind
"yawning": a physiological insight. J Health All
Sci. 2020;10(2):57-62.
17. Palagi E, Celeghin A, Tamietto M, eta l.
The neuroethology of spontaneous mimicry and
emotional contagion in
human and non-human animals. Neurosci
Biobehav Rev. 2020;111:149-65.
18. Thompson SBN, Daly S, Le Blanche A, et
al. fMRI randomized study of mental and motor
task performance and
cortisol levels to potentiate cortisol as a
new diagnostic biomarker. J Neurol Neurosci.
2016;7(2):1-8.
19. Thompson SBN. Communicating with the
motor cortex? Cortisol and yawning as possible
biomarkers for the
detection of neurological disease. J Neurol
Neurosci. 2016;7(53):1-3.
20. Thompson SBN, Richer S. How yawning and
cortisol regulates the attentional network. J
Neurosci Rehab.
2015;2(1):1-9.
21. Tsurumi S, Kanazawa S, Yamaguchi MK.
Infant brain activity in response to yawning
using functional near-infrared spectroscopy. Sci
Rep. 2019;9:10631.
22. Cordoni G, Favilli E,Palagi E. Earlierth
an previously thought: yawn contagion in
preschool children. Dev Psychobiol.
2021;63(5):931-44.
23. WalusinskiO.Historical
perspectives.In:WalusinskiO,editor.TheMysteryofYawninginPhysiologyandDisease.
Frontiers in Neurology and Neuroscience. Basel:
Karger, Switzerland; 2010. 1-21 p.
24. Walusinski O. Popular knowledge and
beliefs. In: Walusinski O, editor. The Mystery
of Yawning in Physiology and Disease. Frontiers
in Neurology and Neuroscience. Basel: Karger,
Switzerland; 2010. 22-5 p.
25. Cronin TG Jr. Yawning and early
manifestation of vasovagal reflex. Am J
Roentgenol. 1988;150(1):209.
26. Walusinski O. Associated diseases. In:
Walusinski O, editor. The Mystery of Yawning in
Physiology and Disease.
Frontiers in Neurology and Neuroscience.
Basel: Karger, Switzerland; 2010. 140-55 p.
27. Krestel H, Bassetti C, Walusinski O.
Yawning - its anatomy, chemistry, role and
pathological considerations. Prog
Neurobiol. 2018;161:61-78.
28. Rothenberg JE. The significance of
repetitive yawning in the emergency patient. A
warning of imminent death or permanent
disability. Am J Emerg Med. 2021;45:510-12.
29. Thompson SBN, Rose K, Richer S. Yawning
with cortisol :examining the neuroscience behind
the Thompson Cortisol Hypothesis for supporting
rehabilitation of neurologically impaired
individuals. J Neurosci Rehab.
2014;1(1):1-11.
30. Brown BJ, Kim S, Saunders H, et al. A
neural basis for contagious yawning. Cur Biol.
2017;27(17):2713-7.
31. Thompson SBN. Hypothesis to explain
yawning, cortisol rise, brain cooling and motor
cortex involvement of
involuntary arm movement in neurologically
impaired patients. J Neurol Neurosci.
2017;8(1):1-5.
32. Pe_rin B, Gogefroy O, Fall S, et al.
Aletrness in young healthy subjects: an fMRI
study of brain region interactivity
enhanced by a warning signal. Brain Cog.
2010;72:271-81.
33. Walusinski O. How yawning switches the
default-mode network to the attentional network
by activating the
