The objective of this study was to investigate the effect of aroma inhalation on salivary cortisol secretion during sleep and after awakening. We used two essential oils that are known to have opposite effects on the behavior of the autonomous nervous system:lavender that induces the parasympathetic nervous system, and jasmine that induces the sympathetic nervous system. These substances were administered to subjects using an olfactometer, by which the volatilized odorants were intermittently delivered through a cannula (first 1 min of each 5-min interval) during the six-hour sleep period. Eighteen male students (aged 20-24 years) participated in the study and received each odorant (lavender, jasmine or scentless air [control]) each night in a counterbalanced order. Saliva samples were collected every 30 min while the subjects were asleep and every 15 min for 1 h after awakening, using proprietary saliva collection equipment. Salivary cortisol level during 15 min after awakening was significantly higher after lavender aroma inhalation compared to jasmine aroma (
p < 0.01) or control (
p < 0.05) inhalation. After lavender aroma inhalation, recovery from subjective fatigue indicated by Profile of Mood States (POMS) score was significantly higher compared to jasmine aroma (
p < 0.05) and tended to be higher compared to control (
p < 0.10). Increased secretion of salivary cortisol is associated with activation of the hypothalamus-pituitary-adrenal (HPA) system. Our results suggest that inhalation of lavender aroma during sleep augments the HPA activity, and may enhance recovery from subjective fatigue upon awakening.
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