Yawning and cortisol levels in multiple sclerosis: Potential new diagnostic tool

•We believe our paper is ground-breaking in terms of presenting a possible link between cortisol fluctuation and yawning.•Many people with MS become regularly fatigued and yawn, and it is known that cortisol may help lower brain temperature.•We present a study of MS participants and healthy controls and show that the link between yawning and cortisol elevation is more pronounced in MS. Yawning is a significant behavioural response and, together with cortisol, is potentially a new diagnostic marker of neurological diseases. Evidence of an association between yawning and cortisol was found which supports the Thompson Cortisol Hypothesis and thermoregulation hypotheses, indication that brain cooling occurs when yawning. 117 volunteers aged 18–69 years were randomly allocated to experimentally controlled conditions to provoke yawning. Thirty-three had been diagnosed with multiple sclerosis. Saliva cortisol samples were collected before and after yawning or after stimuli presentation in the absence of yawning. Hospital Anxiety and Depression Scale, General Health Questionnaire, demographic and health details were collected. Comparisons were made of yawners and non-yawners, healthy volunteers and MS participants. Exclusion criteria: chronic fatigue, diabetes, fibromyalgia, heart condition, high blood pressure, hormone replacement therapy, stroke. Yawners had significant differences between saliva cortisol sample 1 and 2 among healthy participants (p