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Clinical Aromatherapy (Inhalation)
Literature review and initial scoping of the evidence base for the use of essential oils (Lavender and Neroli) in relation to inhalation to combat stress and anxiety (review funded by ERDF, February 2022)
Aromatherapy has a long history for humans and evidence of its use spans multiple centuries and civilizations. The earliest evidence dates to approximately 3500 years BC, historical artifacts provide evidence of use in Egyptian, Indian, Chinese, Greek, Roman, and many other societies.
More recently, aromatherapy is classified into a group of therapies often referred to as complementary and alternative medicines (CAMs). Their use is widespread, with 1 in 5 adults (20%) reporting having visited some form of CAMs in the UK (Easterford et al., 2005), with aromatherapy being the third more popular CAM therapy (Posadzki et al., 2013). Whilst aromatherapy use can be for a wide variety of ailments, a common psychological disorder that it is utilized for is anxiety.
Anxiety is characterized by psychological and physiological symptoms. The psychological symptoms are often focused on excessive worry about one or more topics, these can often appear to outsiders as disproportionate to the threat that may exist. This worry can then lead to disturbed sleep, tiredness, restlessness, difficulty concentrating, irritability, and many others. Physical symptoms can include increase heart rate and/or palpitations, increased perspiration, headaches, muscle aches and soreness, fatigue to name a few (APA, 2013).
Treatment of anxiety had two main approaches in modern medicine. The first intervention is generally one or more psychological therapies, these can include guided self-help (using a book or computer), Cognitive Behavioural Therapy (CBT), Applied Relaxation to name a few. If these interventions prove unsuccessful then a pharmacological intervention may be proposed by a general practitioner (GP) or psychiatrist. Due to potential side effects and stigma, many patients prefer not to take prescribed medication and instead might prefer to first exhaust CAMs approaches first (NHS.UK, 2018). Provided that the anxiety being experienced is not at a critical level, this appears to be a sound approach. Others may wish to explore CAMs therapies as a way of more long-term management of their symptoms, and indeed, aromatherapy lends itself to this as it can be utilized outside of normal treatment modalities.
One of the most common essential oils used by individuals and aromatherapists to treat anxiety is Lavender. Lavender is a genus of plant that has 47 known species, whilst these species differ in a botanical sense, they share similar chemical compounds that give them their well-known aroma, levels of these compounds differs between the species (Cavanagh & Wilkinson, 2002; Cavanagh & Wilkinson, 2005; Koulivand et al., 2013). Lavender’s use as an anxiolytic has been widely documented and studied, in 2019 a large systematic review and meta-analysis was undertaken by Donelli et al. (2019).
This recent, large, and comprehensive systematic review and meta-analysis looked at 65 randomised control trials, and 25 non-randomised control trials, and through meta-analysis showed that inhalation of lavender essential oil significantly reduced anxiety when measured using any validated scale used. This effect was present with both state and trait anxiety indicating its potential effectiveness in both longer-term and short terms instances of anxiety. A cursory search using the keywords “lavender”, “anxiety”, “randomised” for articles since 2020 yielded 1,420 results, many of the higher-ranking searches were already excludable suggesting that there would be very few studies left for review or meta-analysis.
Another systematic review published in the same year searched between the years 2000 and 2018 for randomised control trials (RCT) investigating the anxiolytic effects of lavender (Kang et al., 2019). Twenty-two studies were included in the systematic review and meta-analysis and showed a significant reduction in: anxiety symptoms, systolic blood pressure, heart rate, and salivary cortisol. As with the Donelli et al. (2019) study, no significant reduction in diastolic blood pressure was found. Both reviews place emphasis on the need for higher-quality studies to be undertaken in the validation of lavender as an intervention for anxiety, citing risk of bias and the quality of RCTs that have been conducted, for justification for future higher-quality RCTs to take place. Both reviews also recommend lavender use in some clinical contexts.
Another potential essential oil with anxiolytic effects is Neroli (Citrus aurantium) which is extracted from the blossom of the bitter orange plant using steam distillation (Suryawanshi, 2011). Compared to lavender, neroli has had far less research attention. However, in 2018 a systematic review was undertaken by Mannucci et al. (2018) that analysed the results of 17 studies, eight pre-clinical studies (no control group), and nine clinical studies (with control groups with clinical conditions). Results showed neroli produced an anxiolytic effect in both pre-clinical and clinical studies. Similar, but to a greater extent, to lavender, studies involving neroli are few and far between and their quality is substandard both in methodology and reporting.
The review concludes that more complete and rigorous clinical studies are required. A brief search using the keywords “Citrus aurantium”, “Anxiety”, and “randomised” yielded 924 results, it is unlikely that there is sufficient trial data to attempt a systematic review with meta-analysis at this stage. Instead, the focus here should be on conducting more robust gold standard trials with both clinical and non-clinical samples. Many studies using neroli involve individuals experiencing anxiety because of some other medical issues or intervention (Acute Coronary Syndrome, Intensive Care Patients, laparoscopic cholecystectomy to name a few). There appears to be a demand for studies that investigate clinically anxious individuals (e.g. with a Generalised Anxiety Disorder diagnosis), or a general population sample to see if a significant reduction in sub-clinical symptomology can be achieved.
In conclusion, both lavender and neroli appear to have anxiolytic effects when inhaled. Essential oil blends including these two as predominant oils would likely reduce symptoms associated with anxiety in most individuals. In both instances, further, more robust randomised controlled trials are needed to continue to provide validation for their use clinically.
Diagnostic and statistical manual of mental disorders : DSM-5™, (2013).
Cavanagh, H., & Wilkinson, J. (2002). Biological activities of lavender essential oil. Phytotherapy Research, 16(4), 301-308.
Cavanagh, H. M., & Wilkinson, J. M. (2005). Lavender essential oil: a review. Australian infection control, 10(1), 35-37.
Donelli, D., Antonelli, M., Bellinazzi, C., Gensini, G. F., & Firenzuoli, F. (2019). Effects of lavender on anxiety: A systematic review and meta-analysis. Phytomedicine, 65, 153099 (link)
Easterford, K., Clough, P., Comish, S., Lawton, L., & Duncan, S. (2005). The use of complementary medicines and alternative practitioners in a cohort of patients with epilepsy. Epilepsy & behavior, 6(1), 59-62.
Kang, H.-J., Nam, E. S., Lee, Y., & Kim, M. (2019). How strong is the evidence for the anxiolytic efficacy of lavender?: Systematic review and meta-analysis of randomized controlled trials. Asian nursing research, 13(5), 295-305.
Koulivand, P. H., Khaleghi Ghadiri, M., & Gorji, A. (2013). Lavender and the nervous system. Evidence-Based Complementary and Alternative Medicine, 2013.
Mannucci, C., Calapai, F., Cardia, L., Inferrera, G., D’Arena, G., Di Pietro, M., Navarra, M., Gangemi, S., Ventura Spagnolo, E., & Calapai, G. (2018). Clinical Pharmacology of Citrus aurantium and Citrus sinensis for the Treatment of Anxiety. Evidence-Based Complementary and Alternative Medicine, 2018 (link)
NHS.UK. (2018). Treatment - Generalised anxiety disorder in adults. Retrieved 18/01/2022 from https://www.nhs.uk/mental-health/conditions/generalised-anxiety-disorder/treatment/
Posadzki, P., Watson, L. K., Alotaibi, A., & Ernst, E. (2013). Prevalence of use of complementary and alternative medicine (CAM) by patients/consumers in the UK: a systematic review of surveys. Clinical medicine, 13(2), 126.
Suryawanshi, J. A. S. (2011). An overview of Citrus aurantium used in the treatment of various diseases. African Journal of Plant Science, 5(7), 390-395.
Thanks to Dr. Ashley Bennet (Psychology Dept, University of Bedford) for this literature review (funded by an ERDF Innovation Bridges grant).