Comparison of 30 days inhalational aromatherapy using lavender oil vs. sweet almond oil on Autonomic functions in adults with moderate stress: A Randomized Controlled Trial

Abstract

Background: Stress triggers complex physiological responses mediated through the hypothalamic–pituitary–adrenal (HPA) axis and the autonomic nervous system (ANS). Chronic stress leads to sympathetic overactivity, reduced heart rate variability (HRV), and increased cardiovascular risk. Aromatherapy using lavender oil has shown anxiolytic and parasympathomimetic effects, but limited studies have evaluated its impact on objective autonomic function tests (AFT).

Aim: To compare the effects of lavender oil and sweet almond oil inhalation on autonomic modulation, cardiovascular responses, and perceived stress levels in moderately stressed adults.

Materials and Methods: A randomized controlled trial was conducted on 68 adults with moderate stress (PSS score 14–26). Participants were randomly allocated to Group L (lavender oil) or Group S (sweet almond oil). Both groups underwent daily 30-minute inhalational aromatherapy for 30 days. Baseline and post-intervention assessments included blood pressure, heart rate, HRV (time- and frequency-domain parameters), handgrip test, cold pressor test, 30:15 ratio, and Perceived Stress Scale (PSS). Statistical significance was set at p < 0.05.

Results: Baseline demographic and physiological parameters were comparable between the groups (p > 0.05). After 30 days, the lavender group showed significantly lower systolic and diastolic blood pressure during the handgrip and cold pressor tests (p < 0.01). HRV analysis demonstrated increased HF power, higher pNN50, longer RR intervals, and reduced sympathetic reactivity in the lavender group compared to controls (p < 0.01). The perceived stress score decreased markedly in the lavender group (21.62 ± 5.05 to 11.35 ± 3.41; p < 0.01), whereas minimal change occurred in the control group.

Conclusion: Lavender oil aromatherapy significantly enhances parasympathetic activity, improves HRV indices, reduces cardiovascular reactivity to stress, and lowers perceived stress levels. These findings support lavender aromatherapy as a safe, effective, non-pharmacological intervention for autonomic balancing and stress reduction.