Scents modulate anxiety levels, but electroencephalographic and electrocardiographic assessments could diverge from subjective reports: a pilot study

Abstract

Scents can influence anxiety, including that experienced in clinical environments. This study examined the effects of two distinct aromas: lavender, a fragrance widely recognized for its calming properties, and African stone, a musky and relatively unfamiliar scent. Twenty healthy participants underwent alternating periods of rest and scent inhalation in a dental office environment while anxiety was assessed using the State-Trait Anxiety Inventory (STAI), electroencephalographic (EEG) measures of theta, alpha, and beta power ratios, and electrocardiographic (ECG) measures of heart rate variability (HRV). Lavender inhalation significantly reduced self-reported state anxiety scores but did not produce measurable changes in EEG or HRV indices, possibly due to the short (5 min) exposure duration. African stone, in contrast, did not alter self-reported anxiety but induced significant physiological effects, including reduced theta and, increased alpha power in parieto-occipital regions, and decreased high-frequency (HF) and total HRV power. While the EEG changes are consistent with a more relaxed state, the HRV reductions could indicate a heightened autonomic arousal, suggesting that African stone could have triggered increased attention and physiological activation rather than merely relaxation. These findings demonstrate a divergence between subjective and physiological responses to scent exposure. Lavender appears to primarily reduce perceived anxiety, while African stone influences physiological arousal. We suggest that a multimodal approach be applied in aromatherapy research.

Keywords: EEG; HRV; STAI; anxiety; aromatherapy; dentistry; hyraceum; lavender.

Figure 1

Experimental settings. (A) The layout of EEG recordings. (B) An example of the recorded EEG, ECG, and respiratory signals. (C) Schematics of the experimental protocol.

Figure 2

Spectra and topographic maps of EEG activity (median across participants) during scent inhalation conditions: (A) water, (B) African stone, and (C) lavender. White dots indicate clusters of leads showing statistically significant differences in theta and alpha ratios between African stone and water. Subplots (D,E) show comparisons of (D) theta and (E) alpha power across conditions, averaged over P3, Pz, P4, PO3, PO4, O1, Oz, and O2 leads. Each dot represents an individual participant; lines connect values from the same participant across conditions.

Figure 3

Changes in heart rate variability (HRV) across scent inhalation conditions: water, African stone, and lavender. (A) Average HRV spectra across conditions (mean). (B) High frequency HRV (HF HRV) and (C) total HRV power across conditions. Each dot represents an individual participant; lines connect data points from the same participant. (D) Average HRV spectra across participants with low and high trait anxiety scores from the STAI questionnaire (mean). Subplots (E–H) show relationships between trait anxiety scores and HRV indices: (E) logarithm of low frequency (LF) HRV power, (F) LF to HF ratio, (G) normalized LF HRV power, and (H) normalized HF HRV power. Each dot represents an individual participant.

Figure 4

State anxiety scores from the State–Trait Anxiety Inventory (STAI) questionnaire. (A) State anxiety scores recorded before the experiment and immediately after each odor inhalation (four assessments in total). (B) Baseline-corrected changes in state anxiety following inhalation. (C) State anxiety scores across the experimental session timeline.