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Who Needs Benzos? Lavender and Insomnia
By David Kiefer, MD, Dr. Kiefer is a Clinical Instructor, Family Medicine, at the University of Washington in Seattle; Clinical Assistant Professor of Medicine at the University of Arizona in Tucson, and Adjunct Faculty at Bastyr University in Seattle; he reports no consultant, stockholder, speaker's bureau, research, or other financial relationships with companies having ties to this field of study.
Gordon Lightfoot sang about it, and you have surely seen its beautiful purple flower in gardens or its oil on the shelves of health food stores. Perhaps you have even enjoyed lavender as a part of the flavoring in a gourmet chocolate bar. But does it put you to sleep? This article will attempt to shed light on the topic of lavender and sleep, and comment on whether a simple eye pillow impregnated with lavender is sufficient or, if not, what formulations and doses might be most useful. Read on for the details about a plant whose traditional use is making its way into the modern herbal era.
History and Traditional Use
Lavender, both the whole plant and its isolated essential oil, has a long history of traditional use for a variety of medical conditions: externally for rheumatic conditions; internally for anxiety, insomnia, and gastrointestinal problems; and via aromatherapy for insomnia.1-3 Other, vaguely described uses are for migraines, menstrual cramps, and asthma.3 In addition, there are many properties listed for lavender associated with its essential oils. For example, some sources mention antibacterial, antifungal, and insecticidal actions for lavender oil.4,5
Botany and Pharmacology
Lavender is a member of the mint (Lamiaceae) family, and the most common species used medicinally is Lavandula angustifolia, often referred to as English lavender. Many other names exist, such as common lavender, French lavender, and garden lavender,3 and other scientific names mentioned in the herbal and medical literature include L. officinalis, L. vera, L. spica, L. dentata, L. latifolia, L. pubescens, and L. stoechas.
L. angustifolia is native to the Mediterranean, Russia, Africa, and the Arabian peninsula,1 but is cultivated extensively throughout Europe and the rest of the world. It is a shrub that grows to 2-3 feet tall, and has characteristically fragrant, purple flowers. Lavender oil is produced by steam distilling the fresh flowering tops of L. angustifolia, yielding two main compounds: linalool (20-50% of the essential oil) and linalyl acetate (30-40% of the essential oil), together with numerous other minor oils such as cis-ocimene, terpinene-4-ol, beta-caryophyllene, and lavandulyl acetate.3,6 Other phytochemicals found in lavender include flavonoids, triterpenoids, and coumarins.2
Mechanism of Action
Some animal trials of lavender have begun to elucidate its mechanism of action. Regarding potential gastrointestinal effects, an in vitro study on guinea pig smooth muscle found that linalool acted as a spasmolytic, probably via a rise in intracellular cAMP, and that isolated linalool seemed to act similarly to the whole lavender oil.7
Other researchers have explored the effect of linalool on the excitatory neurotransmitter glutamate, documenting dose-related inhibition of glutamate binding in rat cerebral cortex, which the researchers claim as validation for the fact that linalool-containing plants are often used in traditional medicine as anticonvulsants and hypnotics.8 Another trial tested lavender (diluted 1:60 in olive oil) orally in mice and found sedative effects on a battery of tests, as well as potentiation of the ability of pentobarbital to increase sleep time.5 Other animal research has documented that orally administered lavender acts as a CNS depressant, as an anticonvulsant, and as a potentiator of the effect of chloral hydrate.9
One experiment on mice documented that aerosolized lavender oil (37% linalool, 42% linalyl acetate) caused a distinct decrease in observed motor activity as compared to untreated controls, and that lavender oil, linalool, and linalyl acetate were each able to inhibit the increase in motor activity that occurred when the mice were injected with caffeine.9 The plasma concentration of linalool correlated directly with time after inhalation and was well below levels that the researchers listed from oral and dermal toxicity studies previously published.
There is a paucity of definitive clinical research for the use of lavender and, more specifically, lavender oil aromatherapy for sleep. One single-blind, crossover, randomized pilot study of 10 people with insomnia compared essential oil of lavender flowers to a sweet almond oil placebo for one week each, including a one-week washout period.10 The oils were added to the cartridge of an aerosolizer that ran all night long, providing aromatherapy to the treatment and placebo groups. The lavender group showed a trend toward improvement
(P = 0.07) in sleep quality as per the Pittsburgh Sleep Quality Index. Women, as well as men younger than 39 years old, had a slightly better response to lavender.
A small (n = 4) case series showed that aromatherapy with lavender oil significantly prolonged sleep when compared to baseline in three patients who recently stopped their pharmaceutical hypnotic medications, and even for one patient who wasn't taking any medication for sleep.11
The effects of lavender aromatherapy on humans were explored by one research team who focused on mood, relaxation, alertness, anxiety, EEG changes, and math computational skills in 40 adults randomized to either three minutes of lavender oil or rosemary oil aromatherapy.12 Both groups had less anxiety and felt more relaxed (P < 0.05 and P < 0.001, respectively), but only the lavender group experienced improved mood (P < 0.01). Furthermore, both groups completed the math tasks faster, but only the lavender group improved in math accuracy (P < 0.05). EEG changes in the lavender group suggested increased drowsiness.
Lavender aromatherapy has been studied as a treatment for other maladies, including mood disorders, and to promote overall well-being, sometimes in conjunction with other therapies such as massage or in combination with other essential oils.13,14 For example, 80 healthy women were given either grapeseed oil or lavender oil in a daily bath for two weeks, and were asked to fill out surveys quantifying mood and psychological well-being.14 There was a significant effect on many parameters simply due to the experience of the daily bath, but the lavender group showed improvement in the anger-frustration subset (P < 0.01) and in reduced negative thinking about the future (P < 0.01). Other trials have documented benefits of lavender oil aromatherapy for agitation in dementia patients,15,16 in hospice,17 or in conjunction with bergamot and cedarwood oils to reduce anxiety associated with chemotherapy.18
In a clinical trial of lavender for treatment of depression, lavender tincture showed less of an effect than imipramine tablets, but the combination of lavender tincture and imipramine was more effective than imipramine alone.19 In another study, lavender oil was added to bath water for perineal discomfort after childbirth, though no statistically significant difference was noted as compared to the control group.20
Dosage and Formulation
For insomnia and anxiety, most research has focused on lavender oil administered as aromatherapy, with the exact dose depending on the specific aerosolizer used. One easy and commonly used aromatherapy dosing regimen is 2-4 drops of lavender oil in 2-3 cups of boiling water.1 Most experts recommend against the oral ingestion of essential oils due to potential contact irritation and hepatotoxicity; an infusion of lavender flowers or leaves can be safely ingested orally, however, because such compounds are dilute and presumed safe when not separated and concentrated as purified essential oils. The oral dose as an infusion is 1-2 teaspoons lavender flowers or leaves per cup of boiling water, steeped for 5-10 minutes, strained, and consumed when sufficiently cool.
Adverse Effects, Contraindications, and Drug Interactions
As mentioned above, a significant interaction with the barbiturate pentobarbital was observed in mice.5 There are only rare reports in the literature of central nervous depression with the use of lavender oil aromatherapy in humans.1 Furthermore, one well-respected source lists lavender as a Class I herb, that is, "Herbs which can be safely consumed when used appropriately."21
The acute oral toxicity (LD50) in rats for lavender oil and linalool are 5 g/kg and 2.8 g/kg, respectively, and the acute dermal toxicity in rabbits (LD50) is 5 g/kg and 5.6 g/kg, respectively.9 This would translate into about 350 g of lavender oil, or about 1.5 cups.
Case reports warn of gynecomastia with exposure to lavender oil topically.22 This occurred in a 4-year-old boy with regular use of a lavender herbal balm, a 10-year-old boy using a lavender and tea tree oil shampoo, and a 7-year-old boy with a history of using lavender-scented skin lotion and soap. A possible mechanism for these results was demonstrated by in vitro testing that revealed both estrogenic and anti-androgenic effects of lavender oil on several different cell lines.22 Whether similar concerns will be raised for lavender aromatherapy remains to be seen.
In vitro testing on human skin fibroblasts and endothelial cells showed a dose-dependent toxicity of lavender oil, which the authors postulate may be the mechanism behind the irritation and inflammation (including contact dermatitis) occasionally encountered with many topically applied essential oils, including lavender.23 In Japan, over a nine-year period, the rate of contact dermatitis with exposure to topical lavender oil was 3.7%.24 Interestingly, at the end of the test period, there was a spike in reactivity to lavender oil (13.9% in the last year), which the researchers ascribe to increasing popularity of topical lavender oil. With increased exposure an increased incidence of sensitization among the population may have occurred.
Coumarins are present in the phytochemical analyses of lavender. This class of compounds is relatively common in the plant kingdom and, though chemically
distinct from coumadin (warfarin), may theoretically have blood-thinning activity. Caution is advised in people who are concomitantly taking antiplatelet or anticoagulant medications.
Lavender, whole-plant and oil, has a long history of traditional use for a variety of medical conditions. For insomnia, there are in vitro and animal research data
that suggest effects on neurotransmitter systems and behavior that could signify increased drowsiness and relaxation. These effects have been most significantly documented using lavender oil and its two main constituents, linalool and linalyl acetate. In humans, however, lavender oil aromatherapy has been researched for its hypnotic effect in only three low-quality trials; while initial results are promising, there is a clear need for further, methodologically sound investigation into the potential benefits and risks of lavender. One significant problem associated with lavender aromatherapy research is devising a placebo arm for a fragrant plant like lavender.
Potential adverse reactions should be noted, specifically with respect to topical applications where dermatitis may occur (people may add lavender oil to their pillow, for instance) and, theoretically, when lavender is used concomitantly with other central nervous system depressants. For the former reason, aromatherapy using an aerosolizer is preferred over an eye pillow impregnated with lavender oil; lavender flowers and leaves in an eye pillow would be safe (very unlikely to cause dermatitis because of minimal spread of the oil) but less likely to volatilize the oils enough to lead to clinical effect.
The short-term use of lavender oil aromatherapy can be considered as a treatment for insomnia, provided that other pharmaceutical or dietary supplement central nervous depressants are not also in use. Pay attention to the development of adverse skin reactions and practice caution in people taking blood-thinning medications. There are convincing mechanistic data, in vitro evidence, and animal research for the use of lavender for insomnia, but a paucity of human data exist in this regard. An improvement on the few clinical trials investigating lavender for the management of insomnia will help to refine this recommendation.
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