Reviewed: Huang L, Capdevila L. Aromatherapy improves work performance through balancing the autonomic nervous system. J Altern Complement Med. March 2017;23(3):214-221.
Research studies have shown a correlation between workplace stress and chronic diseases such as heart disease. Lost productivity due to stress is associated with an annual estimated loss of $300 billion for businesses in the United States. Aromatherapy that uses botanical essential oils for stress relief has been studied in a number of controlled clinical trials. Citrus oils such as petitgrain essential oil, which is derived from the distillation of the leaves and green twigs of the bitter orange (Citrus × aurantium, Rutaceae) tree, have been particularly well-studied for their efficacy in aromatherapy. The purpose of this randomized, placebo-controlled study was to determine if aromatherapy with petitgrain oil could improve work performance in a 15-minute computer task.
Forty-two healthy administrative professionals (26-55 years of age) employed at the Autonomous University of Barcelona entered the study. Study endpoints included: (1) time to complete a series of simple forms in a web browser; (2) heart rate variability (HRV), which was determined by FitLab, a mobile application that analyzes heart rate patterns via a Bluetooth-connected chest strap; and (3) subjective ratings on a global feelings scale (with scores ranging from 0 = “very bad” to 10 = “very good”) and detailed scales of mood (Profile of Mood States [POMS]) and anxiety (State-Trait Anxiety Inventory [STAI]).
The inhalation period lasted a total of 40 minutes, and participants began the computer task 15 minutes after the start of the inhalation period. HRV was assessed at baseline, 20 minutes after inhalation began, and 40 minutes after inhalation began. The STAI, POMS, and global feelings questionnaires were administered at baseline and 5 minutes after the inhalation period ended.
According to the authors, “HRV analysis is a valuable, simple, and noninvasive method for analyzing the continuous changes in the sympathetic-parasympathetic balance of the ANS [autonomic nervous system],” which plays a role in stress regulation. (The sympathetic and parasympathetic nervous systems are the two components of the ANS.) Increases in HRV, reductions in task time, and improvements in mood and anxiety scores are all associated with an improved balance of sympathetic and parasympathetic responses, increased levels of attention, and reduced levels of stress.
The petitgrain treatment (Neroly Co. Ltd.; Hong Kong, China) was carried out with an essential oil containing linalyl acetate (45-55%), linalool (20-27%), and myrcene (1-12%) as the main components. The essential oil was diluted to 2% in water and diffused into the air in the room where the subjects, in groups of seven, performed the tasks. The placebo group was exposed in a similar fashion to a diffusion of almond (Prunus dulcis, Rosaceae) oil (Neroly Co. Ltd.), which contains mainly palmitoleic and linoleic acids and is considered to have a neutral smell.
Five subjects were excluded from the analysis because of excessive artifacts in the HRV recordings, and 37 subjects completed the study (20 in the treatment group and 17 in the control group). Demographic parameters did not differ statistically between the groups.
The treatment group had a significantly faster time of completion of the computerized task (17.35 ± 3.13 minutes versus 19.63 ± 3.87 minutes in the placebo group; P = .05). The treatment group also experienced favorable, significant (P = .05 or less) differences in several subscores of HRV compared to placebo. No differences between groups were seen in mood or anxiety scores.
Analysis of HRV results in the petitgrain group indicates an increase in parasympathetic activity and decrease in sympathetic activity at the beginning of the task. The authors suggest that these changes “could produce an improvement of the mental and emotional condition by a combination of reducing the stress level and increasing the arousal level of the participants in terms of attentiveness and alertness.” They propose that the “sympathetic/parasympathetic balance of the ANS” may be the result of a combination effect from various constituents of petitgrain. Linalool, for example, has sedative effects that can induce changes in parasympathetic activity, whereas myrcene may stimulate sympathetic activity by promoting the release of norepinephrine.
The authors note that the study shows the potential for aromatherapy to improve quality of life and performance in the workplace. This study may be one of the first to directly study aromatherapy in the workplace for both task performance and outcomes related to the autonomic nervous response.
Together, the results suggest an increase in arousal and attention during computer tasks aided by aromatherapy. Study limitations include a relatively small sample size, the relative ease to distinguish treatment and placebo, and the short duration of the study. Larger studies with longer, more stressful tasks might be able to better detect differences in global anxiety and mood scores after aromatherapy. Overall, the study adds to the compelling human data using aromatherapy to improve cognitive function and relieve stress.