Journal of Herbal Medicine 40 (2023) 100672

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Journal of Herbal Medicine

journal homepage: www.elsevier.com/locate/hermed

Review article

The anxiolytic effects of Lavandula angustifolia (lavender): An overview of

systematic reviews
Ahmad Shamabadi a, b, 1, Alireza Hasanzadeh b, 2, Ali Ahmadzade a, 3, Hamidreza Ghadimi c, 4,
Mostafa Gholami a, 5, Shahin Akhondzadeh b, *, 6
a
School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
b
Psychiatric Research Center, Roozbeh Psychiatric Hospital, Tehran University of Medical Sciences, Tehran, Iran
c
School of Medicine, Qom University of Medical Sciences, Qom, Iran

A R T I C L E I N F O A B S T R A C T

Keywords: Introduction: Aromatherapy and decoctions of lavender have been traditionally used for their anxiolytic
Anxiety harboring-soothing effects without proper evidence. This study aims to systematically identify and appraise
Herbal medicine systematic reviews on the anxiolytic effects of Lavandula angustifolia (lavender).
Lavender
Methods: The study protocol was published in PROSPERO (CRD42021279573). ISI Web of Science, Scopus,
Medicinal plant
Pharmacognosy
PubMed, Embase, Cochrane Library, CINAHL, Google Scholar, and PROSPERO were searched up to August 2022
Systematic review without any limitation for systematic reviews studying the anxiolytic effects of lavender in humans. The report
from each study as whether or not lavender was anxiolytic was considered the primary outcome. The AMSTAR II
was utilized for the quality assessment.
Results: Thirty systematic reviews met the inclusion criteria, fifteen of which conducted meta-analyses. All studies
were published after 2010 and reported promising effects through different methods of lavender admin­
istration—namely: inhalation, massage, and oral routes—on anxiety relief. Oral doses of 80 mg and 160 mg were
both effective, the higher dose being more efficient. The studies were conducted on various subjects, including
preoperative patients, cardiovascular patients, hemodialysis patients, cancer patients, dental patients, and
women in pre-labor. When assessed by AMSTAR II, four studies were of high quality, one had medium quality,
and the rest were of low or critically low quality. No major adverse event was reported.
Conclusions: Lavender has shown promising potential for anxiety in various settings. Lavender was effective when
inhaled, used as a massage oil, or taken orally. The oral route was the preferred long-term option and inhalation
was recommended for the short term.

1. Introduction physiological perturbations (Park and Kim, 2020; Schuyler, 2016). This
disorder, which is thought to be the most common psychiatric disorder
According to the Diagnostic and Statistical Manual of Mental Dis­ and has been on the rise in recent decades, often remains undertreated,
orders, 5th Edition: DSM-5, anxiety disorders share immoderate feelings leading to feelings of restlessness, early fatigue, impaired concentration,
of fear and anxiety features – as psychological disturbances - and related and an increased risk of cardiovascular disease (Lépine, 2002; Tully

Abbreviations: DSM-5, Diagnostic and Statistical Manual of Mental Disorders, 5th Edition; L. angustifolia, Lavandula angustifolia; SR, systematic review; MA, meta-
analysis; PROSPERO, International prospective register of systematic reviews; AMSTAR, a measurement tool to assess the methodological quality of systematic
reviews; RCT, randomized controlled trial; GAD, generalized anxiety disorder; ICU, intensive care unit; SMD, standardized mean difference.
* Correspondence to: Psychiatric Research Center, Roozbeh Psychiatric Hospital, Tehran University of Medical Sciences, South Kargar Street, Tehran 13337, Iran.
E-mail addresses: a-shamabadi@alumnus.tums.ac.ir (A. Shamabadi), s.akhond@neda.net (S. Akhondzadeh).
1
https://orcid.org/0000–0002-5211–2827
2
https://orcid.org/0000–0002-1041–6080
3
https://orcid.org/0000–0001-6182–4853
4
https://orcid.org/0000–0003-3226–9963
5
https://orcid.org/0000–0003-3509–7415
6
https://orcid.org/0000–0002-2277–5101

https://doi.org/10.1016/j.hermed.2023.100672
Received 20 March 2022; Received in revised form 17 August 2022; Accepted 24 May 2023
Available online 26 May 2023
2210-8033/© 2023 Elsevier GmbH. All rights reserved.
A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

et al., 2016). Anxiety can impose significant morbidity and mortality relevant SRs that were missed. SA had three related SRs in his personal
through functional impairment, decreased quality of life, alcohol and archive. In addition, the references of the included studies and Google
substance abuse, depression, cardiovascular disability, and suicide were manually reviewed and searched, respectively, to find possible
(Bachmann, 2018; Schuyler, 2016; Tully et al., 2016). misses. Title searching in Google Scholar was also done manually,
Owing to the potential effectiveness, tolerability and possible non- focusing on the first 200 citations.
interaction, and low cost, many patients with various diseases seek
traditional and herbal medicine interventions to control and treat dis­
orders. This tendency is higher in patients with psychiatric disorders 2.2. Selection
than in patients without a medical history of psychiatry (Mamtani and
Cimino, 2002). First, duplicate citations were removed using EndNote 20. Then,
Lavandula is an evergreen perennial shrub of the family Lamiaceae references were screened, and studies were selected by AS and AA
that originates from the Mediterranean region (Jianu et al., 2013; Pru­ independently and in parallel. In any case of discrepancy, the senior
sinowska and Śmigielski, 2014). Lavender has received a great deal of author was consulted.
attention from researchers in herbal medicine, and many in-vitro, ani­ Having the following criteria was essential for the eligibility of the
mal, and clinical studies have been conducted on its intervention. Jianu studies: (i) be an SR or MA; (ii) published as full papers in peer-reviewed
et al. (2013) examined the antimicrobial properties of lavender essential journals; (iii) used the words Lavandula or lavender in the title, abstract,
oil. They found a significant bactericidal effect against bacteria such as or keywords; and (iv) investigated the anti-anxiety effects of lavender in
Shigella flexneri, Staphylococcus aureus, and Escherichia coli (Jianu et al., humans.
2013). In another study, Hajhashemi et al. studied the The existence of the following criteria led to the exclusion of studies:
anti-inflammatory and analgesic properties of the leaf extracts and (i) on in-vitro or animal samples; (ii) of any type other than SR and MA;
essential oil of L. angustifolia. They found that some essential oil com­ (iii) no transparent reporting of the study method; (iv) no distinction
ponents can have anti-inflammatory and analgesic effects (Hajhashemi between clinical and pre-clinical studies; and (v) inclusion of fewer than
et al., 2003). A clinical trial conducted on 80 patients with depression three studies with the characteristics required for this study. Indeed, the
disorder treated with citalopram, showed that infusion of 5 g of dried non-specificity of the studies for lavender did not lead to exclusion.
shoots of L. angustifolia had positive therapeutic effects on these patients There was no language limit for inclusion.
and reduced mean depression score (Nikfarjam et al., 2013). A study on If needed, the corresponding authors of the included studies were
patients who wanted to remove their wisdom teeth under local anes­ contacted for further information.
thesia also showed that inhaling lavender essential oil could reduce
peri-operative anxiety (Karan, 2019).
As mentioned earlier, many studies have been conducted to evaluate 2.3. Data extraction
the effectiveness of lavender on various disorders, one of the most
important and notable of which is anxiety. These studies have compiled AS, AH, and AA independently and in parallel extracted the included
data for several systematic reviews (SRs) with or without meta-analysis study data using Review Manager 5.4. Only the included studies were
(MA), assessing the generalizability of the results. These studies had used to extract data—not their references. The senior author’s opinion
been conducted with different methods and qualities affecting their was sought in the absence of a consensus among the extractors.
validity. No study has so far collected and reviewed the evidence The following data were extracted and reported from each study:
generated by these SRs and evaluated their quality. Therefore, this study name of the first author, year of publication, country of study, number of
aims to systematically review SRs with or without MAs investigating the studies included, number of patients studied, follow-up of patients, risk
anxiolytic effects of lavender in humans and to evaluate the methodo­ of bias assessment tool, limitations reported from studies included,
logical quality of the studies conducted. lavender dose as intervention, analysis of results in case of MA, treat­
ment outcome assessment, side effects, the conclusion of effectiveness,
2. Materials and methods and scores of the second version of a measurement tool to assess the
methodological quality of systematic reviews (AMSTAR II). The
2.1. Search conclusion of lavender effectiveness in anxiety reported in each study
was the primary outcome of this study. In the end, the sources of funding
The protocol for this SR was registered and published in the inter­ for the studies included were reviewed by the senior author.
national prospective register of systematic reviews (PROSPERO) under
CRD42021279573. ISI Web of Science Core Collection, Scopus, PubMed,
Embase, Cochrane Library, and CINAHL databases were searched by the 2.4. Quality assessment
first author on September 18, 2021, to obtain the study data. No limi­
tations were considered regarding the time of publication, language, Using the AMSTAR II tool, which is developed for and is highly
document type, and publication status. According to the aim of this reliable in evaluating the methodological quality of SRs and MAs (Shea
study, which was to find and evaluate the SRs and MAs (#1) investi­ et al., 2017); AS, AH, and AA independently and in parallel evaluated
gating the anxiolytic effects (#2) of lavender (#3), the following phrases the quality of the included studies.
established the search strategy: The AMSTAR version used for quality assessment is attached (Ap­
#1 - "systematic review" OR "meta-analysis". pendix A). This version consists of 16 items examining various aspects of
#2 - lavender OR Lavandula. the study quality. There are five two-point and eleven one-point items,
#3 - anxi* (the wild-card term). meaning that a study can have an overall score between zero and 21. Of
The intersection of these three phrases was searched as the final the 16 items in this tool, seven are critical. Details of the score and
search strategy in all the mentioned databases. criticality of each item were specified at the evaluation site. In the
After completing the review text, to cover and include the studies evaluation, if up to one non-critical item is not observed in a study, it
published in the period of about one year, a research was performed on will be reported as a high-quality study. Finding several non-critical
August 1, 2022, with the exact same protocol as the previous one items not observed will be reported as moderate quality study. Low-
(including no limitation in time of publication). The numbers and re­ quality studies did not consider a critical item and critically low-
ports in the results section are from this last search. quality studies did not consider more than one critical item (Shea
PROSPERO was manually searched on August 1, 2022, to include et al., 2017).

2
A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

2.5. Data synthesis 3. Results

Characteristics of the included studies were summarized in a table 3.1. Searching and selecting
and discussed narratively. The number of randomized controlled trials
(RCT) and non-RCT studies included in each review was reported The study selection flow chart is shown in Fig. 1. In total, 195 records
separately. In some instances that studies of essential oils or in­ were obtained through database searching and other sources, which
terventions other than lavender were also included in the reviews, or were all from the personal archives of SA, of which 105 were duplicate
studies of outcomes other than anxiety (assessed by a validated anxiety citations. Subsequently, 90 citations underwent initial screening, the full
scale) were analyzed (such as pain, vital signs, saliva cortisol, etc.), we text of 61 of which needed to be assessed for eligibility and inclusion in
only reported the relevant studies and their corresponding participants this review. After assessing full texts, another 24 references were
in the summarized table. In addition, if the SRs included a risk of bias excluded, and finally, 30 studies were included in this study. The reasons
assessment in their results, the mean score (calculated by summing up for excluding the 31 studies and the characteristics of the 30 studies are
the risk of bias scores of all RCTs (only RCTs that addressed lavender listed in Appendix B and Table 1, respectively. All RCTs included in the
were included) and dividing it by their number) was calculated and thirty systematic reviews are listed in Appendix C.
reported in the characteristics table.
For the studies that had performed MA, the pooled effect data size 3.2. Anti-anxiety effects of lavender
were obtained and summarized in the table. The fraction of primary
studies that favored lavender intervention was reported for those re­ Out of the 30 SRs that were found concerning the effects of lavender
views that did not conduct quantitative analysis. A summary of the on anxiety, MA was conducted in 15 of them. All papers were published
conclusion of each study was also reported in the table. after 2010. Study characteristics and results are summarized in Tables 1
Studies were categorized based on the administration routes and 2. Below, the studies are categorized and discussed narratively,
addressed, and the efficacy of each route for reducing anxiety was dis­ based on the route of administration.
cussed. In addition to the overall effect of lavender on anxiety, any
assessment of effect disparity within genders or different age groups and
any analysis of optimal treatment dosage were reported.

Records identified through databases Additional records identified through

Identification

searching additional sources

(n = 192) (n = 3)

105 duplicates were removed

Screening

Records excluded (n = 29)

Records screened (book, editorial, narrative review,
(n = 90) protocol, clinical trial, non-human
sample, no intervention of interest, no
outcome of interest, corrigendum)

Full-text articles excluded (n = 31)

Full-text articles assessed 2 no type of interest
Eligibility

for eligibility 1 no participant of interest

(n = 61) 2 no intervention of interest
6 no outcome of interest
20 few included studies with
content of interest

Studies included
in qualitative synthesis
Included

(n = 30)

Fig. 1. The study selection flow chart.

3
A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

Table 1
The characteristics of included studies.
First Author, RCT No./ NRT Target population/ NO. of Intervention (number of Control Outcome ROB assessment Average
Year, No. participants trials) tool trial ROB*
Country

Abdelhakim, 4/0 Cardiac surgery patients/ 250 Inhalation (4) Placebo or STAI Cochrane ROB 5.0/7
2019, standard assessment tool
Egypt care
AlMohammed, 23 non- Cardiovascular disease NR NR NR No quality -
2022, differentiated patients/ NR assessment
Saudi Arabia
Amin, 6 non- Coronary angiography Inhalation (6) Placebo or NR No quality -
2022a, differentiated patients/ NR standard assessment
Iran care
Amin, 12 non- Cardiovascular disease Inhalation (12) Placebo, STAI, DASS, BAI No quality -
2022b, differentiated patients/ 878 standard assessment
Iran care, or
active
intervention
Bouya, 3/0 Hemodialysis patients/ 200 Inhalation (3) No HADS, STAI Jadad 3.3/5
2018, intervention
Iran
Cai, 6/2 Dental patient/ 1450 Inhalation (6/2) Placebo or STAI, MDAS, VAS Cochrane ROB 2.6/7
2019, active assessment tool
China intervention
Donelli, 64/25 Anxiety patients, anxiety Inhalation and diffusion Placebo, STAI, Zung SAS, Cochrane ROB 9 LR, 9
2019, inducing (video, pre- (43), massage (10), cap (8), standard HAMA, HADS, SIMA, assessment tool Unclear,
Italy procedure)/ 9123 drink (1), Inhalation and care, or DASS-21, VAS, 46 HR
massage in different arms active POMS, MDAS, BAI,
(1), Shirodhara (1) intervention SPHERE
Ghiasi, 5/0 women during first stage of Inhalation (2), massage (2), Placebo or STAI, VAS Cochrane ROB 2.4/6
2019, labor/ 476 variable (1) standard assessment tool
Iran care
Gong, 12/0 Per-procedure, cancer, burn, Inhalation (9), massage (2), NR STAI Jadad 3.3/7
2020, healthy/ 1001 Inhalation and massage in
China different arms (1)
Guo, 12/0 Pre-surgery patients/ 1132 Inhalation (11), massage Placebo or STAI, VAS, DASS-21 Cochrane ROB 3.6/7
2020, (1) standard assessment tool
China care
Her, 2/3 Cardiac, postpartum, GI, Inhalation (2/1), massage Standard STAI, BAI Joanna Briggs 11/12
2021, chemotherapy, and cancer (0/2) care Institute of
Korea patients/ 294 Critical
Appraisal
checklist
Huang, 7/0 Pre-procedure/ 618 Inhalation (6), massage (1) Placebo or STAI Cochrane ROB 3.8/7
2021, standard assessment tool
China care
Kang, 19/0 Healthy, anxiety patients, pre- Inhalation (13), massage Placebo or STAI, HADS, BAI, Cochrane ROB 4.9/7
2019, procedure, ICU/ 1962 (4), cap (2) standard HAMA, VAS, assessment tool
Korea care
Kavradim, 6/0 Hypertension, coronary heart Inhalation (6) Placebo or STAI, BAI Cochrane ROB 2.4/5
2021, disease, acute coronary standard assessment tool,
turkey syndrome and heart failure (pre care version 2
or post treatment)/ 425
Kim, 30/0 subthreshold anxiety, SAD, Inhalation (21), massage Placebo or STAI, HADS, Cochrane ROB 4.0/5
2021, healthy, cardiac, dental, (5), cap (4) standard DASS-21, VAS, BAI, assessment tool,
Korea hemodialysis, pregnant, care Zung SAS, HAMA, version 2
postpartum, pre-procedure, and MDAS,
pre-surgery patients/ 3906x
Lee, 10/0 Healthy, induced anxiety, Inhalation (5), massage (3), Placebo HADS, SPHERE, NR NR
2011, dementia, pre-procedure, cap (1), variable (1) STAI, HAMA, SF-36
Hong Kong cancer patients/ 24857
Li, 9/0 Cancer patients/ 817 Inhalation (5), massage (3), standard STAI, HADS, Cochrane ROB 3.5/7
2022, both (1) care, or VAS, OAI-23, BAI, assessment tool
China active POMS,
intervention
Mardani, 5/3 Cancer patients/ 533 Inhalation (3/3), massage NR STAI, HADS, VAS, Cochrane ROB NR
2022, (2/0) GAD-7 assessment tool
Iran
Moller, 3/0 Subthreshold anxiety/ 697 Cap (3) Placebo or HAMA Cochrane ROB 6.6/7
2019, active assessment tool
Germany intervention
Moradifar, 20 non- Surgery patients/ 3974 Inhalation (19), massage Placebo, STAI, HADS, VAS, NR NR
2021a, differentiated (1) standard DASS-21, MDAS
Iran care, or
active
intervention
(continued on next page)

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A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

Table 1 (continued )
First Author, RCT No./ NRT Target population/ NO. of Intervention (number of Control Outcome ROB assessment Average
Year, No. participants trials) tool trial ROB*
Country

Moradifar, 8 non- Cardiac patients/ 664 Inhalation (8) Placebo or STAI, DASS-21 NR NR
2021b, differentiated standard
Iran care
Perry, 15/0 Healthy, cancer patients, pre- Inhalation (8), massage (2), Mostly STAI, MDAS, VAS, Jadad 1.4/5
2012, procedure, ICU patients, GAD oil drip (1), oil bath (1), cap placebo, Cox & McKay’s
United or sub subthreshold anxiety/ (3) lorazepam Stress/arousal
Kingdom 1565 for one of adjective checklist,
Silexan HAMA, UMACL,
trials UWIST
Purohit, 4/0 Dental outpatients/ 1146 Inhalation (4) Placebo, STAI, MDAS Cochrane ROB 4.5/7
2021, paroxetine assessment tool
India
Sarris, 3/0 GAD/ 814 Cap (3) NR NR NR NR
2022,
Australia
Sayed, 40/0 Cardiac, induced anxiety, Inhalation (22), massage NR Anxiety on different Cochrane ROB NR
2020, subthreshold anxiety, GAD, (3), cap (7) scales (not specified) assessment tool
Egypt healthy, ICU, hemodialysis,
pregnant, postpartum, pre-
procedure/ 2131
Tabatabaeichehr, 5/0 Labor anxiety/ 1417 Inhalation (3), massage (2) Placebo or VAS, STAI Cochrane ROB 2.4/6
2020, standard assessment tool
Iran care
Trkulja, 6/0 Patients with subthreshold Cap (4) Mostly HAMA NR 5 LR, 1 HR
2020, anxiety, GAD/ 1502 placebo,
Croatia lorazepam,
and other
aroma
Von Känel, 5/0 Patients with subthreshold Cap (5) Placebo, HAMA, SF-36 Cochrane ROB NR
2020, anxiety, GAD/ 1172 lorazepam assessment tool
Switzerland
Yap, 5/0 Anxiety patients/ 1463 Cap (5) Placebo or HAMA Cochrane ROB 5.0/7
2019, active assessment tool
Malaysia intervention
Yeung, 5/0 Anxiety patients/ 1325 Cap (5) Placebo HAMA NR NR
2018,
USA

NR: not reported; RCT: randomized clinical trial; NRT: non randomized trial; ROB: risk of bias; HADS: hospital anxiety and depression score; HAMA: Hamilton anxiety
rating score; SPHERE: somatic and psychological health report; STAI: the state-trait anxiety inventory; SF-36: the short form 36; MDAS: modified dental anxiety scale;
VAS: visual analog scale; PSS: perceived stress scale; UMACL: UWIST mood adjective checklist; BAI: beck anxiety inventory; DASS-21: depression anxiety stress scale-
21; Zung SAS: Zung self-rating anxiety scale; POMS: Profile of Mood States; SIMA: The Single-Item Math Anxiety scale; OAI-23: Ostomy Adjustment Inventory-23; GAD-
7: General Anxiety Disorder-7; ROB: risk of bias; LR: low risk; HR: high risk; GI: gastrointestinal.
*
The average trial ROB for each systematic review was calculated by summing up all the “low risk” scores for all RCTs (only RCTs that addressed lavender against
anxiety were included) and dividing it by the number of RCTs. The denominator in each fraction is the number of bias domains used in each systematic review to assess
RCTs.

3.2.1. Administration routes et al., 2020; Tabatabaeichehr and Mortazavi, 2020), one as medium
(Ghiasi et al., 2019), and the rest four were of high quality (Donelli et al.,
3.2.1.1. Inhalation aromatherapy. Twenty-three studies compared 2019; Huang et al., 2021; Kang et al., 2019; Turan Kavradim et al.,
inhalation aromatherapy to a comparator which mainly consisted of 2021). In most studies, lavender was used as a monotherapy and was not
placebo or standard care (Abdelhakim et al., 2020; Amin et al., 2022a; administered in combination with other conventional anxiolytic drugs.
Amin et al., 2022b; Bouya et al., 2018; Cai et al., 2021; Donelli et al., However, many reviews contained trials where lavender was inhaled as
2019; Ghiasi et al., 2019; Gong et al., 2020; Guo et al., 2020; Her and a blend of several essential oils.
Cho, 2021; Huang et al., 2021; Kang et al., 2019; Kim et al., 2021; Lee As demonstrated in Table 2, 11 studies assessed inhalation aroma­
et al., 2011; Li et al., 2022; Mardani et al., 2022; Moradifar et al., 2021a; therapy without conducting a quantitative analysis (Amin et al., 2022a;
Moradifar et al., 2021b; Perry et al., 2012; Purohit et al., 2021; Sayed Amin et al., 2022b; Bouya et al., 2018; Cai et al., 2021; Ghiasi et al.,
et al., 2020; Tabatabaeichehr and Mortazavi, 2020; Turan Kavradim 2019; Lee et al., 2011; Moradifar et al., 2021a; Moradifar et al., 2021b;
et al., 2021). The target population varied considerably among studies Perry et al., 2012; Sarris et al., 2022; Tabatabaeichehr and Mortazavi,
and included patients with generalized anxiety disorder (GAD) or 2020). Most of the primary trials included in the reviews showed the
sub-syndrome anxiety, healthy patients with trial-induced anxiety, superiority of lavender inhalation over comparators. The smallest frac­
cancer patients, intensive care unit (ICU) patients, pregnant women, tion was presented in a study by Perry et al., where only four out of eight
patients undergoing various procedures such as surgery, dental pro­ included studies favored lavender. None of these studies were of high
cedures, hemodialysis, and chemotherapy. The quality assessment quality.
revealed that five studies were characterized as critically low (Amin In respect of the studies that performed MA, eight studies reported
et al., 2022a,b; Lee et al., 2011; Moradifar et al., 2021a,b), 13 as low the effect size as standardized mean difference (SMD), which ranged
(Abdelhakim et al., 2020; Bouya et al., 2018; Cai et al., 2021; Gong et al., from 0.57 to 1.23, significantly in favor of the lavender intervention
2020; Guo et al., 2020; Her and Cho, 2021; Kim et al., 2021; Li et al., (Donelli et al., 2019; Guo et al., 2020; Her and Cho, 2021; Kang et al.,
2022; Mardani et al., 2022; Perry et al., 2012; Purohit et al., 2021; Sayed 2019; Kim et al., 2021; Li et al., 2022; Sayed et al., 2020; Turan

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A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

Table 2
Results summary of included studies.
First Author, Fraction of studies Meta-analysis Adverse events Conclusion Limitations
Year, favoring lavender
Country intervention

Abdelhakim, - Anxiety (including 1 None Aromatherapy especially lavender Blindness, small sample size, no
2019, non-lavender trial): reduces cardiac surgery anxiety, pain standard dosage
Egypt MD − 3.21 [− 6.08 and HR.
to − 0.35], I2: 90 %
AlMohammed, Aromatherapy (21/23) - NR Lavender significantly improved NR
2022, anxiety
Saudi Arabia
Amin, Inhalation (10/12) - NR Lavender significantly ameliorates the NR
2022b, anxiety signs in some cardiovascular
Iran diseases
Amin-a, Inhalation (6/6) - NR Aromatherapy with lavender Lack of chemical composition and
2022, significantly decreases phytochemical analysis
Iran anxiety in coronary angiography
patients.
Bouya, Inhalation (2/3) - NR Beneficial effects No standard dosage
2018,
Iran
Cai, Inhalation (6/6), - None Aromatherapy is effective and High heterogeneity,
2019, inhalation NRTs (2/2) comparable to music intervention. High ROB
China
Donelli, - Silexan 80 on Headache, All administration methods were Low quality studies, Heterogeneity
2019, HAMA: palpitation, infection, effective in the treatment of anxiety.
Italy MD − 2.90 [− 4.40 GI disorders no effects on BP
to − 0.36], I2: 74 % All non-serious
Silexan 80 on Zung
SAS:
MD − 2.62 [− 4.84
to − 0.39], I2: 17 %
Inhalation on STAI-
S score:
MD − 5.99 [− 9.39
to − 2.59], I2: 95 %
Inhalation on STAI-
T score:
MD − 8.14
[− 14.44 to
− 1.84], I2: 91 %
All lavender
Inhalation:
SMD − 0.73
[− 1.00 to − 0.46],
I2: 85 %
Massage:
SMD − 0.66
[− 0.97 to − 0.35],
I2: 61 %
Ghiasi, Inhalation (2/2), massage - None Positive effects Small sample sizes, methodological
2019, (2/2), variable (1/1) limitations, heterogeneity
Iran
Gong, - Lavender sub group: None Aromatherapy alleviate anxiety A third had high risk of bias, doses
2020, MD: − 7.17 [− 8.06 especially temporary anxiety. were not mentioned, adverse effect
China to − 6.28], I2: 76 % Inhalation was better than massage. were not reported
Guo, - Lavender Subgroup: None Aromatherapy reduces preoperative All cases were elective surgeries,
2020, SMD: − 0.50 anxiety in adults most in middle east (cultural
China [− 0.73 to − 0.27], difference), no standard dosage, high
I2: 63 % ROB, language limitation
Her, - Anxiety: NR Aromatherapy had a significant effect Time and language limitations,
2021, G − 0.93 [− 1.47 to on anxiety
Korea − 0.38], I2: 82 %
Huang, - Lavender sub group: None Aromatherapy as an effective ROB, high heterogeneity
2021, MD − 4.43 [− 8.24 treatment for preoperative anxiety
China to − 0.63], I2: 89 %
Kang, - Relieving anxiety: None Safe anxiolytic effect; both mentally High heterogeneity
2019, G − 0.65 [− 0.84 to and physically
Korea − 0.46], I2:73%
Inhalation
subgroup:
G − 0.71 [− 0.97 to
− 0.45], I2:76 %
Massage subgroup:
G − 0.61 [− 1.06 to
− 0.15], I2:75 %
(continued on next page)

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A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

Table 2 (continued )
First Author, Fraction of studies Meta-analysis Adverse events Conclusion Limitations
Year, favoring lavender
Country intervention

Silexan subgroup:
G − 0.54 [− 0.84 to
− 0.23], I2:54 %
Kavradim, - Anxiety: NR Aromatherapy reduced anxiety, Limited number of included studies,
2021, G 1.23 [0.68–1.78], systolic blood pressure, heart rate and only English language, no standard
turkey I2: 84 % breath rate dosage
Kim, - Anxiety: None inhalation and massage application of ROB, lack of blinding, only English
2021, SMD − 0.72 lavender leads to a significant
Korea [− 0.90 to − 0.55], decrease in anxiety levels
I2: 84 %
Inhalation
subgroup:
G − 0.83 [− 1.03 to
− 0.62]
Massage subgroup:
G − 0.60 [− 1.02 to
− 0.18]
Silexan subgroup:
G − 0.41
[− 0.84–0.03]
Lee, Inhalation (4/5), massage - None Positive and safe effects Different durations, methodological
2011, (1/3), cap (1/1), Variable limitations
Hong Kong (0/1)
Li, - Anxiety (lavender NR Aromatherapy is an effective Only English, Heterogeneity,
2022, subgroup): therapeutic option in alleviating blinding difficulty
China SMD − 1.12 anxiety of cancer patients
[− 1.94 to − 0.31],
I2: 92 %
Mardani, Inhalation (3/3), - None The use of lavender for mitigating ROB, high heterogeneity
2022, inhalation NRTs (2/3), cancer anxiety has been suggested.
Iran massage (1/2)
Moller, - Silexan: Eructation, dyspepsia, Significant anxiolytic effects Limited number of included studies,
2019, MD − 3.83, [− 6.37 allergic skin reactions funding by manufacturers
Germany to − 1.28], I2: 74.7
%
Moradifar, Aromatherapy (18/19), - NR Lavender essential oil has the NR
2021a, massage (1/1) potential to reduce anxiety in patients
Iran undergoing various types of surgery
Moradifar, Aromatherapy (6/8) - NR Lavender is able to significantly NR
2021b, decrease anxiety in patients with
Iran CABG surgery
Perry, Inhalation (4/8), massage - Gastrointestinal Promising but inconclusive effects Methodological limitations,
2012, (0/2), cap (3/3), oil bath problems publication bias
United (0/1), oil drip (0/1)
Kingdom
Purohit, - Dental anxiety None Effective at decreasing patient dental Limited number of the included
2021, level: I2: 1% anxiety studies
India MD − 3.36 [ − 3.77
to − 2.95], I2: 1 %
Sarris, Cap (3/3) - None Lavender is provisionally NR
2022, recommended for GAD
Australia
Sayed, - First week NR Lavender aromatherapy and massage Low quality and small sample size,
2020, Aromatherapy: were the most effective short-term lack of blinding, inadequate
Egypt SMD − 0.57 options. Silexan 80 mg was clinically withdrawal report
[− 1.14 to − 0.01] beneficial for long-term.
Massage:
SMD − 0.20
[− 1.28–0.88]
Silexan 80:
SMD − 0.26
[− 2.12–1.60]
First follow up
Aromatherapy:
SMD − 0.57
[− 0.97 to − 0.16]
Massage:
SMD − 0.20
[− 1.11–0.70]
Silexan 80:
SMD − 0.33
[− 1.11–0.44]
Silexan 160:
SMD − 0.18
(continued on next page)

7
A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

Table 2 (continued )
First Author, Fraction of studies Meta-analysis Adverse events Conclusion Limitations
Year, favoring lavender
Country intervention

[− 1.57–1.21]
Follow up endpoints
Aromatherapy:
SMD 1.79
[0.46–3.12]
Massage:
SMD 0.15
[− 1.56–1.87]
Silexan 80:
SMD − 0.19
[− 1.40–1.02]
Silexan 160:
SMD − 0.20
[− 2.38–1.99]
Tabatabaeichehr, Inhalation (3/3), massage - None Aromatherapy has a positive effect on Small sample size, short intervention
2020, (2/2) pain relief and lowers labor anxiety and f/u
Iran
Trkulja, Cap (5/6) - Gastrointestinal Moderate evidence for short-term NR
2020, problems efficacy
Croatia
Von Känel, - HAMA somatic None Supporting role in anxiety disorders Identical authors, similar effect sizes
2020, anxiety (Items including somatic symptoms
Switzerland 7–13):
SMD − 0.31
[− 0.52 to − 0.10],
I2: 68 %
SF-36 physical
health subscore:
SMD − 0.31
[− 0.44 to − 0.18],
I2: 0%
HAMA insomnia
(Items 4):
SMD − 0.30
[− 0.51 to − 0.10],
I2: 68%
SF-36 vitality
subscore (Fatigue):
SMD − 0.31
[− 0.52 to − 0.10],
I2: 25%
Yap, - Silexan 80: Nausea, eructation, Significant effect of Silexan 160 mg Only English, all in Germany,
2019, MD − 3.820 breath odor and versus placebo, funding by manufacturers
Malaysia [− 5.261 to diarrhea Silexan 80 mg and paroxetine
− 2.380]
Silexan 160:
MD − 4.963
[− 7.167 to
− 2.759]
Yeung, Cap (5/5) - NR Herbal medicines mitigate Publication bias, funding by
2018, anxiety and depression manufacturers, no standard dosage
USA

NR: not reported; NRT: non-randomized trial; RCT: randomized clinical trial; G: Hedges’ G; MD: mean difference; SMD: standardized mean difference

Kavradim et al., 2021). Interestingly, one study showed that lavender Mardani et al., 2022; Moradifar et al., 2021a; Perry et al., 2012; Sayed
inhalation only has significant short-term efficacy, as the calculated et al., 2020; Tabatabaeichehr and Mortazavi, 2020). Comparators
long-term effect size was insignificant (Sayed et al., 2020). The other mainly included standard care or placebo. The number of reviews with
four studies reported mean differences which ranged from 3.21 to 7.17 critically low, low, medium, and high quality on the AMSTAR-II scale
(Abdelhakim et al., 2020; Gong et al., 2020; Huang et al., 2021; Purohit were two (Lee et al., 2011; Moradifar et al., 2021a), nine (Gong et al.,
et al., 2021); however, two of these reviews included a study irrelevant 2020; Guo et al., 2020; Her and Cho, 2021; Kim et al., 2021; Li et al.,
to lavender inhalation in their analysis (Abdelhakim et al., 2020; Gong 2022; Mardani et al., 2022; Perry et al., 2012; Sayed et al., 2020;
et al., 2020). Accordingly, all results significantly favored lavender Tabatabaeichehr and Mortazavi, 2020), one (Ghiasi et al., 2019), and
inhalation, regardless of the study qualities. three (Donelli et al., 2019; Huang et al., 2021; Kang et al., 2019),
respectively. Most of the primary RCTs used lavender in a monotherapy
3.2.1.2. Massage aromatherapy. Massage therapy efficacy was evalu­ massage setting with only four exceptions which were included in
ated in 15 studies in a range of populations such as ICU patients, cancer, studies by Ghiasi et al., Her et al., Kim et al., and Lee et al.
coronary, and burn patients, pregnant women before and after delivery, Out of these studies, six were unable to conduct MA and reported
and pre-procedure patients (Donelli et al., 2019; Ghiasi et al., 2019; their results narratively (Ghiasi et al., 2019; Lee et al., 2011; Li et al.,
Gong et al., 2020; Guo et al., 2020; Her and Cho, 2021; Huang et al., 2022; Moradifar et al., 2021a; Perry et al., 2012; Tabatabaeichehr and
2021; Kang et al., 2019; Kim et al., 2021; Lee et al., 2011; Li et al., 2022; Mortazavi, 2020). Ghiasi et al. (2019), Mardani et al. (2022), and

8
A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

Tabatabaeichehr and Mortazavi (2020) reported the effectiveness of Additionally, in a critically low-quality review, the methods of lavender
lavender massage aromatherapy. Additionally, the only massage trial interventions were not clearly stated, although they concluded that
included in Moradifar et al. (2021a) review favored this therapy. In lavender could significantly improve anxiety (AlMohammed et al.,
contrast, among the relevant trials included in the remaining two re­ 2022).
views, lavender massage was significantly superior to placebo in none
(Perry et al., 2012), or one (Lee et al., 2011) RCT. 3.2.2. Optimal dosage
Two of the high-quality studies quantitatively reported SMDs of 0.61 The number of essential oil drops used for inhalation varied greatly,
and 0.66, significantly favoring lavender massage (Donelli et al., 2019; but most studies used 1–6 drops. The concentration of used solutions for
Kang et al., 2019). Moreover, a low-quality review reported a similar inhalation or massage was rarely noted. No study compared different
SMD of 0.60 (Kim et al., 2021). On the contrary, one low quality re­ dosages of lavender in inhalation or massage setting. Regarding the oral
ported a non-significant effect size for the massage method (Sayed et al., route, 80 mg and 160 mg per day dosage have shown significant efficacy
2020). The other five reviews included too few studies on lavender (Sarris et al., 2022; Trkulja and Barić, 2020; Yap et al., 2019). By con­
massage intervention to justify a separate subgroup analysis (Gong et al., ducting a network MA, one study showed the superiority of the 160 mg
2020; Guo et al., 2020; Her and Cho, 2021; Huang et al., 2021; Li et al., dosage (Yap et al., 2019). However, a network MA in another study
2022). demonstrated that the dose of 80 mg per day was more effective for
long-term treatment (Sayed et al., 2020). In addition, this study rec­
3.2.1.3. Oral administration. 12 studies included RCTs that investigated ommended the inhalation method as the administration route of choice
effects of oral administration of lavender against anxiety (Donelli et al., for short-term treatments. Both of these studies were assessed as low
2019; Kang et al., 2019; Kim et al., 2021; Lee et al., 2011; Möller et al., quality.
2019; Perry et al., 2012; Sarris et al., 2022; Sayed et al., 2020; Trkulja
and Barić, 2020; von Känel et al., 2021; Yap et al., 2019; Yeung et al., 3.2.3. Gender or age differences in efficacy
2018). Except in two studies, all of the investigations on oral lavender The higher prevalence of stress-related psychiatric disorders in
treatment were carried out in a monotherapy setting using Silexan, a women made us explore the relationship between lavender efficacy and
commercial capsule. The two studies were included by Sarris et al. the gender of the recipient. Only two studies addressed this issue (Huang
(2022) and Perry et al. (2012), where the used capsules contained lav­ et al., 2021; von Känel et al., 2021). In the review by von Känel et al.
ender powder or a combination of lavender and sunflower oil, respec­ (2021)the administration of oral lavender capsules in patients with GAD
tively. The target population included healthy volunteers and patients or anxiety was investigated. Treatment effects were not significantly
with GAD or sub-syndrome anxiety. Comparator groups received pla­ different between men and women in this study. In contrast, a subgroup
cebo or active treatments such as lorazepam. Overall quality was criti­ analysis of three studies with exclusively female patients in the review
cally low in six (Lee et al., 2011; Möller et al., 2019; Sarris et al., 2022; by Huang et al. (2021) did not reveal a significant effect size, although
Trkulja and Barić, 2020; von Känel et al., 2021; Yeung et al., 2018), low the overall effect size of the studies was significant.
in four (Kim et al., 2021; Perry et al., 2012; Sayed et al., 2020; Yap et al., In addition, von Känel et al. (2021) found the effects of lavender on
2019), and high in two of the studies (Donelli et al., 2019; Kang et al., anxiety symptoms to be independent of age. No other study investigated
2019). The original RCTs that investigated oral lavender intervention the possible impacts of age of the patient on the results of lavender
overlapped considerably between reviews. treatment.
Four studies did not implement MA to report their results (Lee et al.,
2011; Perry et al., 2012; Trkulja and Barić, 2020; Yeung et al., 2018). 3.3. Quality assessment
Due to the mentioned overlap, the results of these reviews were similar,
and all of them reported a significant efficacy for using Silexan in Table 3 shows each study with its score for the AMSTAR II items.
managing mild to moderate anxiety. Furthermore, in an extensive Based on this tool, only four SRs had high quality, and just one had
clinical guideline systematically investigating the treatment of psychi­ medium quality. Most reviews had low (n = 10) and critically low
atric disorders using nutraceuticals and phytoceuticals, Sarris et al. quality (n = 5).
(2022) found acceptable evidence for implementing oral lavender in
patients with GAD. 4. Discussion
Most of the reviews that performed MA were based on the 80 mg
dosage of Silexan. Four studies summarized their results as SMDs, which 4.1. Summary of evidence
ranged from 0.20 to 0.54, supporting the Silexan treatment (Kang et al.,
2019; Kim et al., 2021; Sayed et al., 2020; von Känel et al., 2021), Through a systematic approach, 30 SRs and MAs evaluating anxio­
though two of them did not find the effect to be significant (Kim et al., lytic effects of lavender in various groups of participants were found, all
2021; Sayed et al., 2020). The other three studies reported mean dif­ of them suggesting lavender as a promising anti-anxiety agent. An SMD
ferences varying from 2.62 to 3.83 (Donelli et al., 2019; Möller et al., ranging from 0.57 to 1.23 was reported for inhalation as the most
2019; Yap et al., 2019). As stated, most of the included original trials investigated route of administration, with 23 reviews addressing it.
were similar among the reviews. Massage therapy was mentioned in 15 reviews, demonstrating an SMD
of around 0.60. The oral route was also investigated in 12 studies, with
3.2.1.4. Other routes. Three reviews included routes of administration SMDs ranging from 0.20 to 0.54, suggesting the efficacy of 80 mg and
other than the above mentioned methods (Ghiasi et al., 2019; Lee et al., 160 mg Silexan capsules in mild to moderate anxiety.
2011; Perry et al., 2012). Perry et al. (2012) included two RCTs where
effects of lavender oil dripping and oil bath on anxiety scales were 4.2. Other implications
assessed in healthy populations, though none of these methods proved
superior to placebo. Ghiasi et al. (2019) and Lee et al. (2011) each As mentioned earlier, studies of lavender, similar to other natural
included one of the two RCTs of the same author that have investigated products that have polyvalent activities reported on them, have not been
the effects of various essential oils, including lavender, in pre-labor limited to anxiety disorders. Lavender has other scientific implications,
women using different administration methods such as inhalation, and there are also many reports of the effects of lavender intervention on
massage, foot bath, birthing pool, and acupressure points. Only the other psychiatric disorders. An SR of seven RCTs concluded that lav­
study in the review by Ghiasi et al. (2019), reported significant results. ender had antidepressant effects in patients with a definitive diagnosis.
However, its prescription is not recommended for treating depression

9
 A. Shamabadi et al.
Table 3
The quality assessment of the included studies based on the AMSTAR II tool.
First Author, year Item 1 Item 2* Item 3 Item 4* Item 5 Item 6 Item 7* Item 8 Item 9* Item 10 Item 11* Item 12 Item 13* Item 14 Item 15* Item 16 Quality
(0–1) (0–2) (0–1) (0–2) (0–1) (0–1) (0–2) (0–2) (0–2) (0–1) (0–1) (0–1) (0–1) (0–1) (0–1) (0–1)

Abdelhakim, 2019 1 1 1 1 1 1 2 2 2 0 1 0 0 1 0 1 L
AlMohammed, 2022 1 0 0 1 1 0 0 1 0 0 - - 0 0 - 1 CL
Amin, 2022a 1 0 0 0 1 1 0 1 0 0 - - 0 0 - 1 CL
Amin, 2022b 1 0 0 0 0 0 0 1 0 0 - - 0 0 - 1 CL
Bouya, 2018 1 1 1 2 1 1 2 2 1 0 - - 0 0 - 1 L
Cai, 2019 1 1 1 1 1 1 0 2 2 0 - - 1 0 - 1 L
Donelli, 2019 1 2 1 1 1 1 2 2 2 0 1 1 1 1 1 1 H
Ghiasi, 2019 1 1 0 1 1 1 2 2 2 0 - - 1 1 - 1 M
Gong, 2020 1 1 1 1 0 0 2 2 2 0 1 1 0 1 1 1 L
Guo, 2020 1 1 1 1 1 1 2 2 2 0 1 1 0 1 1 1 L
Her, 2021 1 2 0 1 1 1 0 1 2 0 1 1 1 1 1 1 L
Huang, 2021 1 1 1 2 1 1 2 2 2 0 1 1 1 1 1 1 H
Kang, 2019 1 1 1 1 1 1 2 2 2 0 1 1 1 1 1 1 H
Kavradim, 2021 1 1 1 2 1 1 2 2 2 0 1 1 1 1 1 1 H
10

Kim, 2021 1 2 0 1 1 1 0 1 2 0 1 1 1 1 1 1 L
Lee, 2018 0 1 1 1 1 0 0 2 2 0 - - 0 0 - 1 CL
Li, 2022 1 2 0 1 1 1 0 1 2 0 1 1 1 1 1 1 L
Mardani, 2022 1 1 0 1 1 1 0 1 2 0 - - 1 0 - 1 L
Moller, 2017 0 0 1 0 0 0 1 2 2 1 1 1 1 1 0 1 CL
Moradifar, 2021a 1 1 0 0 1 1 0 1 1 0 - - 1 0 - 1 CL
Moradifar, 2021b 1 1 0 0 1 1 0 1 0 0 - - 0 0 - 1 CL
Perry, 2012 1 1 1 1 1 1 2 2 2 0 - - 0 1 - 1 L
Purohit, 2021 1 1 1 2 1 1 2 2 2 0 1 1 0 1 1 1 L
Sarris (2022) 1 1 1 1 1 1 0 1 0 0 - - 0 0 - 1 CL
Sayed, 2020 1 1 1 1 1 1 1 1 2 0 1 0 1 1 0 1 L
Tabatabaeichehr, 2020 1 1 1 1 1 1 1 1 2 0 - - 0 0 - 1 L
Trkulja, 2020 1 1 1 0 0 0 0 2 2 0 - - 0 0 - 0 CL
Von Kanel, 2020 1 1 1 0 0 0 0 2 2 0 1 0 0 0 0 1 CL
Yap, 2019 1 1 1 1 1 1 1 2 2 1 1 1 1 1 0 1 L
Yeung, 2018 0 0 1 1 1 1 2 2 0 0 - - 0 0 - 1 CL

Journal of Herbal Medicine 40 (2023) 100672

H: high; M: moderate; L: low; CL: critically low.
*
Critical domains
A. Shamabadi et al. Journal of Herbal Medicine 40 (2023) 100672

yet (Shamabadi and Akhondzadeh, 2021). A study showed that comfort, they should first be thoroughly studied.
concomitant use of lavender essential oil and psychotropic drugs has In addition, it should be noted that many clinical trials consider
been more effective than psychotropic medications alone for treating intervention as an effective one based on statistical analysis when the p-
dementia (Mascherona et al., 2021). Watson et al. (2019) performed an value is less than 0.05. At the same time, the intervention may not be
RCT of L. angustifolia and lemon balm (Melissa officinalis) essential oils clinically significant because minimal changes can lead to statistically
intervention to treat agitated behavior in older people with and without significant results. Even a minor change in the total score of a scale
dementia. They showed that L. angustifolia effectively reduces agitation might be statistically significant, but it is not necessarily clinically
in patients with dementia but has a low effect on patients without de­ visible (Hengartner and Plöderl, 2018).
mentia (O’Connor et al., 2013). Another study revealed that inhaled
lavender improves the quality and quantity of sleep as well as the quality 5. Conclusions
of life in patients with diabetes mellitus type II (Lari et al., 2020).
All of the 30 reviews included demonstrated the effectiveness of
4.3. Low methodological quality of the included studies lavender as an anxiolytic in various populations, including preoperative,
cardiovascular, hemodialysis, cancer, and dental patients and pre-labor
Version II of AMSTAR is the most recent update for AMSTAR and women. Lavender aromatherapy seems to be a safe and tolerable
would be a critical point of view (Shea et al., 2017). In this review, method, showing anti-anxiety properties when inhaled, administered
AMSTAR II showed that most studies did not have acceptable quality. orally, or used as a massage oil. The most common complication was
Considering the fact that AMSTAR II has a precise reviewing platform, it mild gastrointestinal problems, and no other major adverse effect was
is a justifiable tool for judging the quality of SRs. Unfortunately, most of reported. No gender or age preference was reported in any of the studies.
the studies found and included had low or critically low quality; Given the variability of dosages and conflicting results, no definitive
therefore, their results and conclusions should be treated with caution. conclusion on optimal dosage was possible. The most reported effect size
was for the inhalation method, though evidence implied that inhalation
4.4. Significant limitations of core studies is most effective for the short term while the oral route is preferable for
longer treatment durations. Due to the lack of dose standardization and
Due to the breadth of this topic, which entails the exclusion of dis­ low overall quality of the reviews, implementing further trials and re­
cussion of all sub-topics, and the importance of paying attention to the views with better qualities and standardized treatment methods is
limitations and drawbacks of previous studies, some of the most critical recommended.
limitations of core studies included in the 20 SRs are shortly mentioned
and discussed. Funding
Herbal medicines were widely used in the past and were later
replaced by modern medicines (Yuan et al., 2016). They have attracted This study was supported by a grant from Tehran University of
interest again lately because of their potential to treat diseases with Medical Sciences (TUMS) to Professor Shahin Akhondzadeh (grant
probable minor side effects (Li and Weng, 2017; Yuan et al., 2016). number 56403). TUMS had no role in the design, conduct, data collec­
However, like current conventional medications, medicinal plants tion, data interpretation, manuscript preparation, review, final
should be approved via the long-established scientific approach. In the approval, and the decision to submit the paper for publication.
first stage, a pre-clinical trial has to be performed. Subsequently, three
phases of clinical trials must be conducted (in each phase, the effects and Author contribution
side effects are evaluated). Eventually, the medications become publicly
available, and their side effects will be re-evaluated (Eder and Herrling, A.S.: Conceptualization, Methodology, Investigation, Data curation,
2015). In this regard, a committee of the European Medicines Agency is Writing—original draft preparation, Writing—review and editing, Su­
responsible for issuing information on the uses and safety of herbal pervision, Project administration; A.H.: Data curation, Writing—origi­
medicinal products (Knöss and Chinou, 2012). nal draft preparation; A.A.: Data curation, Writing—original draft
Lavandula may be known by a specific name in some countries, and preparation, Writing—review and editing; H.G.: Writing—original draft
each region has a particular lavender with different micromorphological preparation; M.G.: Writing—original draft preparation, Writing—re­
and phytochemical characteristics (Kahkeshani et al., 2014). For this view and editing; S.A.: Supervision, Project administration, Software,
reason, buying plants from open markets, as seen in some studies, re­ Resources, Funding acquisition.
duces the likelihood of achieving reliable results. Although Lavandula is
endemic to the northern Mediterranean region, its different species and Declaration of Competing Interest
subspecies are found in different countries (Edwards et al., 2015).
Consequently, clinical studies should investigate and mention the spe­ The authors declare that they have no known competing financial
cies and characteristics of the plant used. interests or personal relationships that could have appeared to influence
Not mentioning the part of the plant used and not performing an the work reported in this article.
accurate standardization are other remarkable limitations in the core
studies. It is necessary to prepare the ingredients and constituents in Acknowledgments
specific proportions and use them in studies to achieve reliable and
reproducible results (Shamabadi and Akhondzadeh, 2021). Linalool and None.
linalyl acetate are the main ingredients in lavender essential oil. Other
important ingredients in lavender include 1,8-cineole, camphor, and
Appendices A–C. Supporting information
endo-borneol (Jianu et al., 2013). Although the beneficial and harmful
ingredients cannot be identified and studied in the first few studies on a
Supplementary data associated with this article can be found in the
medicinal plant, their identification will be easier with the proper
online version at doi:10.1016/j.hermed.2023.100672.
standardization and characterization.
As mentioned, L. angustifolia has been used in studies and adminis­
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