Aroma Effects on Physiologic and Cognitive Function Following Acute Stress: A Mechanism Investigation

Abstract

Objective: Aromas may improve physiologic and cognitive function after stress, but associated mechanisms remain unknown. This study evaluated the effects of lavender aroma, which is commonly used for stress reduction, on physiologic and cognitive functions. The contribution of pharmacologic, hedonic, and expectancy-related mechanisms of the aromatherapy effects was evaluated.

Methods: Ninety-two healthy adults (mean age, 58.0 years; 79.3% women) were randomly assigned to three aroma groups (lavender, perceptible placebo [coconut], and nonperceptible placebo [water] and to two prime subgroups (primed, with a suggestion of inhaling a powerful stress-reducing aroma, or no prime). Participants' performance on a battery of cognitive tests, physiologic responses, and subjective stress were evaluated at baseline and after exposure to a stress battery during which aromatherapy was present. Participants also rated the intensity and pleasantness of their assigned aroma.

Results: Pharmacologic effects of lavender but not placebo aromas significantly benefited post-stress performance on the working memory task (F(2, 86) = 5.41; p = 0.006). Increased expectancy due to positive prime, regardless of aroma type, facilitated post-stress performance on the processing speed task (F(1, 87) = 8.31; p = 0.005). Aroma hedonics (pleasantness and intensity) played a role in the beneficial lavender effect on working memory and physiologic function.

Conclusions: The observable aroma effects were produced by a combination of mechanisms involving aroma-specific pharmacologic properties, aroma hedonic properties, and participant expectations. In the future, each of these mechanisms could be manipulated to produce optimal functioning.

Conflict of interest statement

Author Disclosure Statement No competing financial interests exist.

Figures

FIG. 1.

Consolidated Standards of Reporting Trials diagram.

FIG. 2.

Study activities.

FIG. 3.

Post-stress cognitive performance: aroma groups (A) and prime subgroups (B). The data are presented as mean percentage difference from baseline performance, with the untransformed mean values presented for easier interpretation. Error bars represent standard errors of the mean (SEM). Positive difference on Digit Span Backward (DSB) and Letter-Number Sequencing (LNS) tasks indicates improvement, and on simple reaction time (SRT) and Golden Stroop (GS) task indicates deterioration in performance. **p ≤ 0.01 for the between-group differences.

FIG. 4.

Post-stress physiologic functioning by aroma group: Cortisol (A), Respiration (B), and Chromogranin A (C). The data are presented as percentage change from baseline value in an untransformed form to allow for easier interpretation. All physiologic measures were significantly different from baseline at stress time point. **p < 0.01 for the time differences (change from baseline).