Bergamot ( Citrus bergamia ) Essential Oil Inhalation Improves Positive Feelings in the Waiting Room of a Mental Health Treatment Center: A Pilot Study: Essential Oil Inhalation Improves Positive Feelings

Abstract

Mental health issues have been increasingly recognized as public health problems globally. Their burden is projected to increase over the next several decades. Additional therapies for mental problems are in urgent need worldwide due to the limitations and costs of existing healthcare approaches. Essential oil aromatherapy can provide a cost-effective and safe treatment for many mental problems. This pilot study observed the effects of bergamot essential oil inhalation on mental health and well-being, as measured by the Positive and Negative Affect Scale, in a mental-health treatment center located in Utah, USA. Fifty-seven eligible participants (50 women, age range: 23–70 years) were included for analysis. Fifteen minutes of bergamot essential oil exposure improved participants' positive feelings compared with the control group (17% higher). Unexpectedly, more participants participated in experimental periods rather than control periods, suggesting even brief exposure to essential oil aroma may make people more willing to enroll in clinical trials. This study provides preliminary evidence of the efficacy and safety of bergamot essential oil inhalation on mental well-being in a mental health treatment center, suggesting that bergamot essential oil aromatherapy can be an effective adjunct treatment to improve individuals' mental health and well-being. © 2017 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd.

Full text

Bergamot (Citrus bergamia) Essential Oil
Inhalation Improves Positive Feelings in the
Waiting Room of a Mental Health Treatment
Center: A Pilot Study
Xuesheng Han,
1
*Jacob Gibson,
2
Dennis L. Eggett
3
and Tory L. Parker
1
1
dōTERRA International, LLC, 389 South 1300 West, Pleasant Grove, UT 84062, USA
2
The Green House Center for Growth and Learning, 135 West Center Street, Pleasant Grove, UT 84062, USA
3
223 TMCB Brigham Young University, Provo, UT 84602, USA
Mental health issues have been increasingly recognized as public health problems globally. Their burden is
projected to increase over the next several decades. Additional therapies for mental problems are in urgent need
worldwide due to the limitations and costs of existing healthcare approaches. Essential oil aromatherapy can
provide a cost-effective and safe treatment for many mental problems. This pilot study observed the effects of
bergamot essential oil inhalation on mental health and well-being, as measured by the Positive and Negative
Affect Scale, in a mental-health treatment center located in Utah, USA. Fifty-seven eligible participants
(50 women, age range: 23–70 years) were included for analysis. Fifteen minutes of bergamot essential oil
exposure improved participants’positive feelings compared with the control group (17% higher). Unexpectedly,
more participants participated in experimental periods rather than control periods, suggesting even brief
exposure to essential oil aroma may make people more willing to enroll in clinical trials. This study provides
preliminary evidence of the efficacy and safety of bergamot essential oil inhalation on mental well-being in a
mental health treatment center, suggesting that bergamot essential oil aromatherapy can be an effective adjunct
treatment to improve individuals’mental health and well-being. © 2017 The Authors. Phytotherapy Research
published by John Wiley & Sons Ltd.
Keywords: bergamot essential oil; aromatherapy; mental well-being; mental health; positive affect; negative affect.
INTRODUCTION
Mental health disorders have been increasingly
recognized as public health problems globally (Kessler
et al., 2015). Mental health disorders include abnormally
high levels of anxiety, depression, stress, cognitive
impairment, insomnia, and so on. Of note, the prevalence
of stress-related symptoms among the working class has
been increasing across a wide variety of occupations
(Baba et al., 1999; Johnson et al., 2005; McCarthy et al.,
2016). The health impact of mental disorders is both
immediate and long term. The immediate health effects
relate to overall well-being, quality of life, work
performance, and social interactions (McCarthy et al.,
2016). Long-term health effects can lead to chronic
diseases and premature death (Andrews and Carter,
2001). A recent World Health Organization (WHO)
World Mental Health survey (N= 52 095) (Bruffaerts
et al., 2015) found a consistent association between pre-
existing mood (odds ratio = 1.3–1.4), anxiety (odds
ratio = 1.2–1.7), and the subsequent onset of headaches.
The WHO Global Burden of Disease Study (Bruffaerts
et al., 2015) estimates that mental disorders are among
the most burdensome in the world, and their burden will
increase over the next 4 decades. The current healthcare
system has inadequately addressed individuals with
mental disorders. This includes a lack of good
operational propositions, lack of professionalism, low
quality of care, and improper pharmaceutical
prescriptions (Mercier et al., 2010). Almost all prescribed
drugs for mental disorders come with a long list of side
effects (Jones and Lal, 1985; Bantz et al., 1987; Etzel,
1994; Gerlach and Larsen, 1999; Schaefer et al., 2003;
Rummel-Kluge et al., 2010). Alternative therapies for
mental disorders are in urgent need worldwide.
The inhalation of essential oils may provide a cost-
effective, safe, and appropriate therapy for some mental
disorders. Many human studies involving a wide
diversity of patients and healthy volunteers have
successfully shown significant positive effects of
lavender essential oil (Moss et al., 2003; Toda and
Morimoto, 2008; Hongratanaworakit, 2011; Seifi et al.,
2014) on stress relief, anxiety reduction, mood
improvement, and depression relief. Chemical analysis
of lavender essential oil shows a complex mixture of
naturally occurring phytochemicals, including linalool
and linalyl acetate (Prashar et al., 2004). It has been
suggested that the major components in essential oils
contributing to anti-anxiety and anti-depressant effects
are linalool (Linck et al., 2010), limonene (Lima et al.,
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium,
provided the original work is properly cited.
* Correspondence to: Xuesheng Han, dōTERRA International, LLC, 389
South 1300 West, Pleasant Grove, UT 84062, USA.
E-mail: lhan@doterra.com
Contract/grant sponsor: dōTERRA International, LLC.
[Correction added on 06 April 2017, after first online publication: Contract/
grant sponsor has been corrected in this version].
PHYTOTHERAPY RESEARCH
Phytother. Res. 31: 812–816 (2017)
Published online 24 March 2017 in Wiley Online Library
(wileyonlinelibrary.com) DOI: 10.1002/ptr.5806
© 2017 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd.
Received 28 November 2016
Revised 19 January 2017
Accepted 27 February 2017

2013), and pinene (Satou et al., 2013). Reasonably, it has
been proposed that essential oils with a high content of
these compounds could have anxiolytic and anti-
depressant effects as well.
Bergamot essential oil (hereafter BEO) has a long
industrial and medicinal history (Navarra et al., 2015).
It is characterized by a high content of limonene,
linalool, and linalyl acetate. Several clinical studies on
aromatherapy with BEO, in combination with other
essential oils, have shown promising results: anxiety
and stress reduction, anti-depression, pain relief, and
blood pressure and heart rate reduction. Further human
studies with BEO inhalation alone have also shown
significant effects on anxiety reduction (Watanabe
et al., 2015), depression reduction (Watanabe et al.,
2015), and blood pressure (Chang and Shen, 2011; Ni
et al., 2013) and heart rate reduction (Chang and Shen,
2011; Ni et al., 2013). In addition, BEO has minimal side
effects, if any (Navarra et al., 2015), suggesting BEO
inhalation may have potential therapeutic benefits
including improving overall mental health and anxiety.
We explored the effect of BEO inhalation on
participants’mental well-being and feelings in the lobby
of a mental health treatment center prior to receiving
treatment. Participants’mental health was measured by
a self-rated questionnaire: The Positive and Negative
Affect Schedule (PANAS), a standardized, well-validated
outcome measurement (Watson et al., 1988). PANAS has
been shown to be an effective measurement for
momentary mental health and well-being, incorporating
both positive and negative dimensions of mood (Watson
et al., 1988; Crawford and Henry, 2004). It has also been
widely used to evaluate individuals’mood states in a
variety of situations (Crawford and Henry, 2004).
METHODS
This study was conducted in the waiting room of a
mental health treatment center (The Green House
Center for Growth and Learning, Pleasant Grove,
UT, USA). Participants were current patients of the
center or patients’companions. This study was
reviewed and approved by an institutional review
board (IRB) before commencement.
Inclusion and exclusion criteria. Both women and men,
aged between 18 and 70 years, were included if they
could communicate verbally and read and write in
English. Women who were pregnant and/or lactating
were excluded. People with no sense of smell or with
known pre-existing sensitivities to essential oils were
excluded from the study. Patients who, judged by the
staff of the treatment center as not good candidates for
the study, were also excluded.
Procedure. The trial lasted 8 weeks. Weeks 1, 3, 5, and 7
were essential-oil diffusion periods; weeks 2, 4, 6, and 8
were distilled-water diffusion periods. Participants who
met the above eligibility criteria and agreed to
participate were instructed to sit as still as possible in
the waiting room for 15 min. Written consent was
waived per an IRB’s evaluation. Depending on the
week they came to the center, they were exposed to
either bergamot or distilled water aromatically. Patients
were told the study was intended to assess the waiting
time’s effect on mental feelings to distract their
attention from the smell in the waiting room. After
15 min, participants were asked to complete the PANAS
survey and demographic information (Fig. S1). Then,
they could proceed with their regularly scheduled
treatment. Any adverse events were also recorded.
Study instruments and materials. The aromatherapy
devices were four waterless diffusers, provided by
dōTERRA (Pleasant Grove, UT, USA), and placed out
of sight of the participants in the waiting room. The gas
chromatography–mass spectrometry analysis of BEO
showed that its major chemical constituents (i.e., >5%)
are limonene (36%), linalyl acetate (31%), linalool
(11%), gamma-terpinene (8%), and beta-pinene (7%).
The diffusers were turned on 15 min before the first
patient arrived and kept running at half speed throughout
the day. The speed setup of diffusers and their locations
were selected based on previous experiments
(unpublished data), ensuring that a comfortable and
consistent aroma was maintained through the day. Facility
staff routinely checked each diffuser to ensure there was
always sufficient essential oil or distilled water, and
replaced new bottles of oil or water if needed. This
ensured that each participant received an equivalent
strength and amount of oil aroma or water vapor during
the 15-min study period, which approximately mimicked
the real-life scenario of aromatic usage of essential oils.
The PANAS has been extensively validated and
utilized to assess momentary mental well-being (Watson
et al., 1988; Crawford and Henry, 2004). It consists of 20
items (e.g. ‘interested’and ‘distressed’), and respondents
rate the intensity of their feelings about each item at that
moment from 1 (very slightly or not at all)to5(extremely).
Ten items assess respondents’positive feelings, while the
other ten assess negative feelings. Scores range from 10
to 50 for either positive or negative affect. The PANAS
typically takes less than 5 min to complete.
Statistical analysis. Fifty-nine participants completed the
study. Two were missing scores for one or more of the
PANAS items; therefore, they were excluded from
analysis. The age range was 23–58 years for the BEO
group, and 23–70 years for the control group (Table 1).
Most participants (50 out of 57) were female and
Table 1. Participant’s demographic information
Active group (n) Control group (n)
Participants 45 12
Women 38 12
Men 7 0
Women’s age range (years) 23–58 23–70
Men’s age range (years) 36–48 n/a
Caucasian 41 12
Non-Caucasian 4 0
Female and Caucasian 36 12
Patients 10 0
813ESSENTIAL OIL INHALATION IMPROVES POSITIVE FEELINGS
© 2017 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd. Phytother. Res. 31: 812–816 (2017)

Caucasian. Among these, only ten of them were current
patients of the treatment center (the others were
patients’companions).
Data were analyzed using the Statistics Analysis
Software System (SAS Institute Inc., Cary, NC, USA).
The analysis compared the difference between the
active group (BEO) and the control group (distilled
water) in positive and negative affect scores. In addition,
a two-sample t-test was also performed for each
individual item to compare the means for each
treatment group. Statistical assessments were two tailed
and considered significant at p<0.05 and near
significance at 0.05 ≤p<0.1.
RESULTS
No adverse effects were caused by exposure to BEO
aroma as reported by the participants. More
participants participated and completed the trial in the
active group (n= 45) than did those in the control group
(n= 12) (Table 1). There were ten patients in the active
group and none in the control group.
Overall, the active group reported both higher
positive and negative affect scores than did the control
group (Table 2). The mean positive affect score for the
active group was 17% higher than that of the control
group, although the improvement was not considered
statistically significant. The mean negative affect score
for the active group was 15.4% higher than that of the
control group, and the increase was not statistically
significant either. A complete listing of all statistical tests
is contained in Table 2.
No statistically significant difference was observed
for any of the individual items between the active
group and control group (Table 2). However, near-
significant (0.05 <p<0.1) and meaningful differences
(0.4 or above on a scale from 1 to 5) were observed for
several items. Participants in the active group reported
a 48.77% higher score of feeling ‘proud’compared
with the control group. They also reported a 43.36%
higher score of feeling ‘active.’However, participants
in the active group also reported a 60% increase of
feeling ‘nervous.’
DISCUSSION
Participants in the waiting room of the mental health
treatment center in the BEO group reported higher
positive affect scores than did the control group.
Participants in the BEO group also showed a smaller
increase in negative affect scores than did the control
group; however, the reasons why are unclear. It could
be due to an effect resulting from the smaller size of
the control group. Interestingly, the control group’s
mean negative affect score was already in the very
lower end of the scale. This indicates that there was
probably not much room to improve in negative affect,
partially because the clear majority of participants (47
out of 57) were patients’companions, who were less
likely to have mental disorders than patients.
Moreover, the improvement in positive affect scores
was greater than the increase in negative affect scores,
although neither of them was statistically significant.
Collectively, this suggests that BEO aromatherapy
Table 2. Summary of PANAS scores in the active group and the control group (N= 57)
Item
Active
group mean
(n= 45)
Active
group SE
(n= 45)
Control
group mean
(n= 12)
Control
group SE
(n= 12)
Difference
(active control)
SE
of
difference
Degrees
of
freedom
t-test
value p-value
Positive
affect
1 Interested 2.73 0.18 2.75 0.35 0.02 0.39 55 0.04 0.97
3 Excited 1.69 0.12 1.42 0.24 0.27 0.26 55 1.03 0.31
5 Strong 2.60 0.18 2.33 0.36 0.27 0.31 55 0.67 0.51
9 Enthusiastic 2.22 0.18 1.92 0.35 0.31 0.38 55 0.79 0.44
10 Proud 2.36 0.19 1.58 0.37 0.77 0.41 55 1.87 0.07*
12 Alert 3.13 0.16 2.67 0.30 0.47 0.34 55 1.38 0.17
14 Inspired 2.38 0.18 1.83 0.35 0.54 0.39 55 1.39 0.17
16 Determined 2.93 0.19 2.58 0.37 0.35 0.41 55 0.84 0.40
17 Attentive 2.91 0.15 2.83 0.30 0.08 0.33 55 0.23 0.82
19 Active 1.91 0.14 1.33 0.28 0.58 0.31 55 1.86 0.07*
Total positive 24.87 1.15 21.25 2.22 3.62 2.5 55 1.45 0.15
Negative
affect
2 Distressed 1.91 0.17 1.50 0.33 0.41 0.37 55 1.12 0.27
4 Upset 1.53 0.14 1.42 0.28 0.12 0.31 55 0.38 0.71
6 Guilty 1.38 1.14 1.50 0.27 0.12 0.31 55 0.40 0.69
7 Scared 1.60 0.16 1.00 0.31 0.60 0.35 55 1.70 0.10
8 Hostile 1.16 0.08 1.33 0.16 0.18 0.18 55 1 0.32
11 Irritable 1.62 0.15 1.75 0.29 0.13 0.32 55 0.39 0.70
13 Ashamed 1.31 0.15 1.42 0.29 0.11 0.33 55 0.32 0.75
15 Nervous 1.73 0.16 1.08 0.30 0.65 0.34 55 1.92 0.06*
18 Jittery 1.60 1.50 1.33 0.29 0.27 0.33 55 0.82 0.42
20 Afraid 1.57 0.16 1.00 0.30 0.57 0.34 55 1.67 0.10
Total negative 15.38 1.09 13.33 2.12 2.04 2.4 55 0.86 0.40
Note: SE, standard error; PANAS, The Positive and Negative Affect Schedule.
*p<0.1.
814 X. HAN ET AL.
© 2017 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd. Phytother. Res. 31: 812–816 (2017)

might provide beneficial effects on participants’mental
well-being and feelings, as measured by PANAS, in the
waiting room of a mental health treatment center.
A body of clinical research has provided evidence
supporting the therapeutic effects of BEO
aromatherapy on mild mental disorders in a variety
of settings (Navarra et al., 2015). Bergamot essential
oil aromatherapy provided several beneficial effects
to participants including reduced heart rate, blood
pressure, stress responses, depression, and anxiety
(Chang and Shen, 2011; Ni et al., 2013; Navarra
et al., 2015; Watanabe et al., 2015). Although the
BEO mechanism is not fully understood, some studies
suggest that it may trigger the release of discrete
amino acids, which then may act as neurotransmitters
that interact with normal and pathological synaptic
plasticity (Bagetta et al., 2010; Saiyudthong and
Marsden, 2011). The clinical pharmacology of BEO is
out of this study’s scope; however, it was recently
reviewed by Mannucci and colleagues (Mannucci
et al., 2017).
Bergamot essential oil aromatherapy was extremely
safe in this study, and no adverse events were reported.
This was largely consistent with existing literature
(Navarra et al., 2015; Mannucci et al., 2017). This might
be partially true because bergamot and other citrus
aromas are common; therefore, people have become
used to these aromas.
To our knowledge, this study provided the first
evidence of the therapeutic efficacy and safety of BEO
aromatherapy in the waiting room of a mental health
treatment center. Although definite conclusions of
BEO’s therapeutic properties remain elusive, BEO
aromatherapy may play an important role in a holistic
healthcare approach, especially for those dealing with
issues related to mental health or well-being (Mannucci
et al., 2017).
It is unclear why fewer people were willing to
participate during the control periods than the BEO
periods (ns = 12 vs. 45). This observation appears to
be more apparent for patients of the mental health
treatment center, who had already been diagnosed with
mental health issues: ten patients participated in the
BEO periods, while no patient participated in the
control periods. To the best of our knowledge, this is
unlikely due to any other interventions than the
difference between exposure to BEO aroma and water
vapor. One explanation would be that even very brief
exposure to BEO aroma may somehow make people
(specifically patients with mental issues) become more
willing to participate in clinical trial in the current
setting. If this is true, it can have profound applications
in both clinical trial participation and compliance as well
as many other scenarios.
LIMITATIONS
This study had several limitations. It was designed as a
pilot study to explore the potential benefits of BEO
aromatherapy for mental well-being and feelings. The
study did not have sufficient statistical power to make
definite conclusions mainly due to the small control
group, small overall study size, and study design. The
study design was the best possible option at the time
the trial commenced. We designed it to mimic the real-
life scenarios of aroma inhalation as much as possible.
Furthermore, we intended to minimize the effects that
the treatment center had on the trial and its participants.
Therefore, only current patients of the center and their
companions were invited to participate. Further studies
with designs, such as better controlling participation,
are recommended.
Acknowledgements
The authors acknowledge the Green House Center (Pleasant Grove,
UT, USA) for allowing us to conduct the study at their facility.
Conflicts of Interest
X.H. and T.P. are employees of dōTERRA (Pleasant
Grove, UT, USA), where the Bergamot essential oil
was manufactured. D.E. is a consulting statistician for
dōTERRA.
REFERENCES
Andrews G, Carter GL. 2001. What people say about their general
practitioners’treatment of anxiety and depression. Med J Aust
175(Suppl): S48–S51.
Baba VV, Galperin BL, Lituchy TR. 1999. Occupational mental
health: a study of work-related depression among nurses in
the Caribbean. Int J Nurs Stud 36: 163–169.
Bagetta G, Morrone LA, Rombolà L, et al. 2010. Neuropharmacology
of the essential oil of bergamot. Fitoterapia 81: 453–461.
Bantz EW, Dolen WK, Chadwick EW, Nelson HS. 1987. Chronic
chlorpheniramine therapy: subsensitivity, drug metabolism,
and compliance. Ann Allergy 59: 341–346.
Bruffaerts R, Demyttenaere K, Kessler RC, et al. 2015. The
associations between preexisting mental disorders and
subsequent onset of chronic headaches: a worldwide
epidemiologic perspective. J Pain 16:42–52.
Chang K-M, Shen C-W. 2011. Aromatherapy benefits autonomic
nervous system regulation for elementary school faculty in
taiwan. Evid-Based Complement Altern Med 2011: 946537.
Crawford JR, Henry JD. 2004. The positive and negative affect
schedule (PANAS): construct validity, measurement properties
and normative data in a large non-clinical sample. Br J Clin
Psychol 43: 245–265.
Etzel JV. 1994. Diphenhydramine-induced acute dystonia.
Pharmacotherapy 14: 492–496.
Gerlach J, Larsen EB. 1999. Subjective experience and mental
side-effects of antipsychotic treatment. Acta Psychiatr Scand
Suppl 395:113–117.
Hongratanaworakit T. 2011. Aroma-therapeutic effects of
massage blended essential oils on humans. Nat Prod Commun
6: 1199–1204.
Johnson S, Cooper C, Cartwright S, Donald I, Taylor P, Millet C.
2005. The experience of work-related stress across
occupations. J Manag Psychol 20: 178–187.
Jones B, Lal S. 1985. Tardive dyskinesia uncovered after ingestion of
Sominex, an over-the-counter drug. Can J Psychiatry Rev 30:
370–371.
Kessler RC, Sampson NA, Berglund P, et al. 2015. Anxious and
non-anxious major depressive disorder in the World Health
Organization World Mental Health Surveys. Epidemiol
Psychiatr Sci 24: 210–226.
815ESSENTIAL OIL INHALATION IMPROVES POSITIVE FEELINGS
© 2017 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd. Phytother. Res. 31: 812–816 (2017)

Lima NGPB, De Sousa DP, Pimenta FCF, et al. 2013. Anxiolytic-like
activity and GC-MS analysis of (R)-(+)-limonene fragrance, a
natural compound found in foods and plants. Pharmacol
Biochem Behav 103:450–454.
Linck VM, da Silva AL, Figueiró M, Caramão EB, Moreno PRH,
Elisabetsky E. 2010. Effects of inhaled Linalool in anxiety,
social interaction and aggressive behavior in mice.
Phytomedicine 17: 679–683.
Mannucci C, Navarra M, Calapai F, Squeri R, Gangemi S, Calapai G.
2017. Clinical pharmacology of Citrus bergamia: a systematic
review. Phytother Res 31:27–39.
McCarthy JM, Trougakos JP, Cheng BH. 2016. Are anxious
workers less productive workers? It depends on the quality
of social exchange. J Appl Psychol 101: 279–291.
Mercier A, Kerhuel N, Stalnikiewitz B, et al. 2010. Obstacles to
effective treatment of depression. A general practitioners’
postal survey in the north-west region of France. Encéphale
36(Suppl 2): D73–D82.
Moss M, Cook J, Wesnes K, Duckett P. 2003. Aromas of rosemary
and lavender essential oils differentially affect cognition and
mood in healthy adults. Int J Neurosci 113 :15–38.
Navarra M, Mannucci C, Delbò M, Calapai G. 2015. Citrus
bergamia essential oil: from basic research to clinical
application. Front Pharmacol 6: 36.
Ni C-H, Hou W-H, Kao C-C, et al. 2013. The anxiolytic effect of
aromatherapy on patients awaiting ambulatory surgery: a
randomized controlled trial. Evid-Based Complement Altern
Med 2013: 927419.
Prashar A, Locke IC, Evans CS. 2004. Cytotoxicity of lavender oil and
its major components to human skin cells. Cell Prolif 37:
221–229.
Rummel-Kluge C, Komossa K, Schwarz S, et al. 2010. Head-to-head
comparisons of metabolic side effects of second generation
antipsychotics in the treatment of schizophrenia: a systematic
review and meta-analysis. Schizophr Res 123: 225–233.
Saiyudthong S, Marsden CA. 2011. Acute effects of bergamot oil
on anxiety-related behaviour and corticosterone level in rats.
Phytother Res 25: 858–862.
Satou T, Takahashi M, Kasuya H, et al. 2013. Organ accumulation
in mice after inhalation of single or mixed essential oil
compounds. Phytother Res 27: 306–311.
Schaefer M, Schmidt F, Folwaczny C, et al. 2003. Adherence and
mental side effects during hepatitis C treatment with
interferon alfa and ribavirin in psychiatric risk groups. Hepatol
Baltim Md 37: 443–451.
Seifi Z, Beikmoradi A, Oshvandi K, Poorolajal J, Araghchian M,
Safiaryan R. 2014. The effect of lavender essential oil on
anxiety level in patients undergoing coronary artery bypass
graft surgery: a double-blinded randomized clinical trial. Iran
J Nurs Midwifery Res 19: 574–580.
Toda M, Morimoto K. 2008. Effect of lavender aroma on salivary
endocrinological stress markers. Arch Oral Biol 53:
964–968.
Watanabe E, Kuchta K, Kimura M, Rauwald HW, Kamei T, Imanishi
J. 2015. Effects of bergamot (Citrus bergamia) essential oil
aromatherapy on mood states, parasympathetic nervous
system activity, and salivary cortisol levels in 41 healthy
females. Forsh Komplementmed 22:43–49.
Watson D, Clark LA, Tellegen A. 1988. Development and
validation of brief measures of positive and negative affect:
the PANAS scales. J Pers Soc Psychol 54: 1063–1070.
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© 2017 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd. Phytother. Res. 31: 812–816 (2017)