The increase in urinary serotonin and decrease in salivary cortisol concentrations following direct inhalations of concentrated essential oils is not induced by non-specific effects

Abstract

Abstract Objectives. The effectiveness of exogenously triggered serotonin (e.g., dietary supplements, drugs) increase is varied. However, since urinary serotonin concentrations were found to correlate with those in the cerebrospinal fluid, the olfactory system might be an efficient and testable pathway to quickly elevate serotonin levels due to its fast-acting central neurophysiological and peripheral pathways. However, little research has been devoted to investigate this assumption. This paper extends previous findings of parasympathetic activation of a specially designed essential oil inhaler (AromaStick® Balance) by experimentally testing its impact on urine serotonin and saliva cortisol excretion. Method. Two experiments involving healthy individuals were conducted to test the efficacy of essential oil application to the nose by employing different inhalation protocols and control conditions. Results. In the pilot study (n=8), serotonin urine excretion was increased after six inhalations (effect size Cohen’s d=0.7). In the second experiment (n=80), inhalations proved superior to both the natural control condition and the pseudo placebo condition after three and six inhalation cycles (0.6<d<1.8). In addition, there was a large reduction of cortisol saliva levels after three inhalations (d=0.9). Conclusion. Short and deep inhalations of essential oil scents directly delivered to the olfac-tory system appear to result in an enhanced serotonin and a reduced cortisol release in healthy individuals of both sexes.