Simon B N Thompson and Mia Simonsen
Yawning apparatus and exact location of the yawn reflex remains controversial. Yet yawning is a significant behavioural response and potentially a new diagnostic marker of neurological disease. Association between cortisol, electromyography (EMG) and yawning was found in humans supporting Thompson Cortisol Hypothesis (TCH) which complements thermoregulation hypotheses indicating brain cooling occurs when yawning. 28 male, 54 female volunteers, 18-69 years, randomly allocated to experimentally controlled conditions of provoked yawning. Saliva samples were collected at start and after yawning, or after stimuli presentation, in absence of yawning. EMG data was collected from jaw muscles at rest and after yawning. Specially designed yawning susceptibility scale, Hospital Anxiety and Depression Scale, General Health Questionnaire, demographic, health details were collected. Between- and within-subjects comparisons of yawners and non-yawners was conducted. Exclusion criteria: chronic fatigue, diabetes, fibromyalgia, heart condition, high blood pressure, hormone replacement therapy, multiples sclerosis, stroke. Yawning group: significant difference between saliva cortisol samples, rest and yawning t (37)=2.842, p=0.007, compared with non-yawners, rest and post-stimuli, which was non-significant. Yawners, rest EMG: -100 to 200 millionth of a volt (mean=182.2) and -60 000 to 18 000 (mean=3 897.4) after yawning. Non-yawners, rest EMG: -80 to 120 (mean=37.2) and -400 to 800 (mean=57.5) after stimuli presentation. Yawners showed larger peak following yawn compared with post-stimuli for non-yawners. Significant supporting evidence for TCH suggests cortisol levels are elevated during yawning. Changes in cortisol levels may become a new diagnostic tool in early diagnosis of neurological symptoms. Bournemouth University Research & Ethics BU-KAPP06-09/13.
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