Lavender may have a role in treating anxiety but no firm conclusions can be drawn without higher quality, less biased studies, a large systematic review and meta-analysis suggests.
"Oral lavender in the form of a standardized essential oil titrated in linalool and linalyl acetate may be helpful as an add-on therapy, or in reducing the dosages, and, therefore, the side effects of common anxiety drugs like benzodiazepines," study investigator Davide Donelli, MD, Careggi University Hospital, Florence, Italy, told Medscape Medical News.
"It would be premature to consider lavender essential oil inhalation as a treatment for anxiety on the basis of our findings," Donelli added.
The study is published in the December issue of Phytomedicine.
High Anxiety in America
The Anxiety and Depression Association of America estimates that anxiety disorders affect 40 million adults, or 18% of the US population, every year, making such disorders the most common mental illnesses nationwide.
Lavender is often suggested as an ancillary treatment for anxiety largely because of its storied past as a natural anxiolytic.
To assess its efficacy, the researchers examined studies that included lavender (in any form or method of administration) and its effect on anxiety and anxiety-related conditions.
The analysis included 65 randomized controlled trials (RCTs) with a total of 7993 participants and 25 nonrandomized studies (NRSs) with 1200 participants in a qualitative synthesis; in addition, the researchers analyzed 37 RCTs with 3964 participants in a quantitative synthesis.
In the qualitative analysis, 54 RCTs reported "at least a significant result" in favor of lavender for anxiety, either as a significant improvement from baseline within intervention groups, or as a significant post-test amelioration of anxiety levels in intervention groups compared with control groups.
In the qualitative analysis of NRSs, 17 studies indicated a significant improvement in at least one anxiety measure within intervention groups, or a significant post-test difference between intervention and control groups, when present, in favor of lavender.
In the quantitative analysis, oral lavender (80 mg per day for at least 6 weeks) had a significant effect in diminishing anxiety levels based on the Hamilton Anxiety Scale (mean difference, −2.90; 95% confidence interval [CI], −4.86 to −0.95; P = .004) and the Zung Self-rating Anxiety Scale (mean difference, −2.62; 95% CI, −4.84 to −0.39; P < .05).
High Risk of Bias
Massage with lavender oil also appeared helpful for reducing anxiety (Hedges' g = −0.66; 95% CI, −0.97 to −0.35; P < .0001). However, the studies are not sufficient to determine with certainty whether the benefit is because of a specific effect of lavender, thus impeding from clearly differentiating it from the beneficial effect of massage, the authors note.
Lavender inhalation also appeared to reduce anxiety levels (Hedges' g = −0.73; 95% confidence interval [CI] −1.00 to −0.46; P < .00001), including state and trait anxiety.
Given that it is "simple, safe and inexpensive," it could be considered in certain clinical situations, Donelli told Medscape Medical News.
However, the investigators caution that the available studies are of "low average quality" with most characterized by a "high overall risk of bias." The heterogeneity of study designs, especially with regard to non-oral ways of administration, is another limitation of the analysis, they note.
"To increase certainty, it would be advisable to perform some more high-quality randomized controlled trials," said Donelli.
"Novel trials ought to be designed with a more standardized approach, especially when the studied intervention is lavender oil inhalation rather than its oral administration, because, to date, studies on this topic are very heterogeneous from a medical point of view," he added.
CBT the Best Choice
Commenting on the findings for Medscape Medical News, Luana Marques, PhD, clinical psychologist and associate director of the Center for Anxiety and Traumatic Stress Disorders at Massachusetts General Hospital, Boston, said the study was well done and noted the "results highlight the concern we still have in clinical care, which is the original studies have a lot of bias."
Based on available data, "it's hard to say whether lavender is helpful or not for anxiety. It is promising in that some studies suggest that it may be helpful, especially for mild anxiety but not severe levels of anxiety, but the data are not conclusive by any stretch," said Marques, who was not involved with the systematic review and meta-analysis.
"The bottom line is that it shouldn't be used as first-line treatment for anxiety. My first go-to is cognitive behavioral therapy (CBT), which is an evidenced-based treatment," she added.
The study had no specific funding. Donelli and Marques have disclosed no relevant financial relationships.
Phytomedicine. Published online September 26, 2019. Full text
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Cite this: Lavender Promising for Anxiety but Evidence Base Needs to Grow - Medscape - Nov 15, 2019.