Lavender flower and its extracts have been used, both internally and by olfaction, for centuries as a treatment for anxiety and depression. Modern analytical research has identified the main active constituents of the oil; in vitro and animal studies have begun to elucidate mechanisms of action; and controlled clinical trials in humans now document lavender’s efficacy, safety, and dose.
Anxiety is a common complaint and may range from every day stress to clinically relevant symptoms requiring medical intervention. Patients with generalized anxiety disorder (GAD) can experience excessive anxiety and worry associated with the stresses of everyday life. Most cases of GAD begin in childhood and can lead—without treatment—to a chronic condition, with fluctuating symptoms, often exacerbated by stressful life events. Disturbed sleep has been observed to be among the most frequent accompanying disorders of generalized anxiety. Individuals with anxiety disorder not otherwise specified (AD NOS) also present with clinically significant symptoms, but they tend to report less worry, negative affect, depression, and comorbidity than those with GAD.
The most commonly prescribed agents in the medical treatment of anxiety are benzodiazepines and selective serotonin reuptake inhibitors (SSRIs).The well-known side effects of benzodiazepines include drowsiness, fatigue, confusion and disorientation, dizziness, decreased concentration, impaired memory, dry mouth, and blurred vision. Benzodiazepines can impair the ability to drive or operate machinery and may thus interfere with essential activities of daily living. They lower the tolerance to alcohol and are widely reported to cause physical and psychological dependence and withdrawal symptoms. SSRIs, on the other hand, may cause sedation and fatigue, gastrointestinal disturbances, agitation or insomnia. The risks and inconveniences associated with available anxiolytic pharmaceutical medications may be one of the reasons anxiety disorder is considered an undertreated condition.
Herbal preparations have long been a mainstay for treating anxiety and depression. Some botanical agents, most notably kava (Piper methysticum), have demonstrated efficacy for clinically diagnosed anxiety disorders. Others, such as St. John’s wort (Hypercom perforatum), are clinically efficacious for depression in most, though not all, clinical studies. Kava, however, has been withdrawn by many manufacturers due to concerns over potential hepatotoxicity, even though these effects may have been primarily due to drug interactions, misuse, and poor quality extracts of this otherwise well-tolerated phytomedicine; St. John’s wort’s popularity has suffered because it was found to stimulate cytochrome P450 34, an enzyme that metabolizes at least half of the known pharmaceuticals sold today. A safe, non-sedating, non–habit forming herbal anxiolytic with proven efficacy for GAD and depression is, therefore, of interest to clinicians. Throughout history, lavender has been cultivated for its flowers and oils and used both cosmetically and medicinally. A member of the Labiate family, lavender is primarily used either dried or as an essential oil. Historical use includes documented activity as an antibacterial, antifungal, carminative, sedative, and antidepressant. Lavandula angustifolia, Mill. is the most common species of lavender utilized for health purposes. Lavender is native to the Mediterranean, the Arabian Peninsula, Russia, and Africa.
Lavender has a high concentration of volatile oils, which impart its distinctive and pleasing fragrance. The relaxing experience of lavender fragrance led to its deliberate, therapeutic use in aromatherapy to relieve mild anxiety. Lavender has been also used internally for mood imbalances such as anxiety, insomnia, and gastrointestinal distress, including “nervous stomach.”
Lavender essential oil is obtained from steam distillation processing of the flowering tops of L. angustifolia. Modern analytical methods, such as capillary gas chromatography, have demonstrated that lavender oil contains more than 160 constituents, many of which interact synergistically to contribute to its healing effects. The main active constituents of lavender oil are linalool, linalyl acetate, terpinen-4-ol, and camphor. The quantity of the linalyl acetate is determined by the method of steam distillation as it degrades upon distillation to yield linalool. The highest content of linalyl acetate is obtained when fresh lavender flowers are steam distilled right after harvest. Other constituents found in lavender include: cis-ocimene; terpinen-4-ol, ß-caryophyllene; lavandulyl acetate; 1,8-cineole; and small amounts of limonene, geraniol, lavandulol, ß-pinene, camphene, geranyl acetate, and neryl acetate.
Relative amounts of bioactive constituents can vary significantly from one lavender oil to another. The European Pharmacopoeia includes limits or ranges for the content of the predominant components. Specifically, oils with high concentrations of esters and low concentrations of cineol and other minor components are generally considered to be of higher quality because these parameters indicate that a gentle and careful production process was applied and that high quality raw materials were used. A high quality lavender extract would not only comply with this monograph but would ideally exceed those specifications with a higher content of linalyl acetate (ideally 33–45%) and lavandulyl acetate (≥1.5%), and a lower limit for the content of cineol (≤2 %).
Mechanisms of action
In vitro and in vivo studies have demonstrated multiple possible mechanisms of action of lavender oil, as well as its individual constituents, which may partly account for its relaxing effects when taken orally. Lavender oil has potentiated expression of GABA-A receptors in cell culture;it has shown spasmolytic activity on guinea pig ileum; linalool, a main active ingredient of lavender oil, has been shown in animals to inhibit glutamate binding in the brain;linalool has also inhibited acetylcholine release and influenced ionic conductance in neurons;linalyl acetate is described to exert a relaxing effect. Lavender oil has reduced dose-dependently spontaneous motility and caffeine-induced hyperactivity of mice.Lavender oil aromatherapy has been shown to be effective in the management of anxiety and depression and small and medium-sized controlled and uncontrolled clinical trials.
Much prior research on lavender has focused on the administration of lavender via an olfactory route. The anxiolytic activity of lavender olfaction has been demonstrated in several small and medium-sized clinical trials.The efficacy of aromatherapy of lavender is thought to be due to the psychological effects of the fragrance combined with physiological effects of volatile oils in the limbic system. These calming effects of lavender oil and single constituents may be the origin of the traditional use of lavender. Lavender oil olfaction has been shown to decrease anxiety, as measured by the Hamilton rating scale, and can increase mood scores.The following are selected examples of clinical trials on lavender aromatherapy:
- Dunn and colleagues demonstrated anxiolytic activity of lavender oil aromatherapy in patients in intensive care units. Subjects received at least 1 session of aromatherapy with 1% lavender essential oil. Significant anxiolytic effects were noted in the 1st treatment, though 2nd and 3rd treatments did not appear to be as effective.
- Alaoui-Ismaili and colleagues found that the aroma of lavender is considered by subjects to be very pleasant and is correlated with changes in the autonomic nervous system.
- Tysoe and colleagues conducted a study of lavender oil in burner use on staff mood and stress in a hospital setting. A significant number of respondents (85%) believed that lavender aroma improved the work environment following the use of the lavender oil burners.
- Diego and colleagues demonstrated that people receiving lavender oil (10%) olfaction for 3 minutes felt significantly more relaxed and had decreased anxiety scores, improved mood and increased scores of alpha power on EEG (an indicator of alertness), and increased speed of mathematical calculations.
- Lewith and colleagues investigated the effects of lavender aromatherapy on depressed mood and anxiety in female patients being treated with chronic hemodialysis. The effects of aromatherapy were measured using the Hamilton rating scale for depression (HAMD) and the Hamilton rating scale for anxiety (HAMA). Lavender aroma significantly decreased the mean scores of HAMA, suggesting an effective, noninvasive means for the treatment of anxiety in hemodialysis patients.
- Lavender aromatherapy, with or without massage, may also reduce the perception of pain and the need for conventional analgesics in adults and children, though more rigorously controlled trials are needed.