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Kava Extract
Relieves Anxiety: Meta-Analysis
To perform a meta-analysis, researchers
select the best of available clinical trials, then review and
combine the results, allowing them to draw conclusions with more
confidence than would be possible from isolated studies. For a
meta-analysis of trials on kava (Piper methysticum G. Forster.,
Piperaceae), researchers at the University of Exeter, UK, selected
three out of 14 double-blind, randomized, placebo-controlled clinical
trials (Pittler et al., 2000). Their results help confirm
the validity of the individual kava studies: Compared with placebo,
kava extract is an efficacious treatment for anxiety. The three
trials were selected based on their use of the same outcome measurement
(the standard Hamilton Rating Scale for Anxiety, or HAM-A) and
inclusion criteria (a baseline HAM-A score of 19 or higher), as
well as the type and dosage of the kava preparation tested (300
mg/day of extract standardized to deliver a total daily dose of
70 percent kavapyrones, i.e., 210 mg). All three trials utilized
the same kava extract, WS 1490 (Laitan®, manufactured by W. Schwabe,
Karlsruhe, Germany). Results of the meta-analysis demonstrated
a significant reduction in anxiety scores as measured by the HAM-A.
The scientists noted that these findings are supported by the
results of the largest randomized clinical trial in their database
(Volz et al., 1997), and that the results were similar to those
of kava clinical research in general. Patients in the three studies
took 100 mg three times daily of kava extract for up to 24 weeks,
and analysis suggested a "significant reduction in the HAM-A total
score of approximately 10 points in favor of kava extract." In
none of the studies did placebo rate higher than kava in reducing
anxiety.
According to U.S statistics, around 17
percent of the population experiences anxiety disorders in any
one year, and the lifetime prevalence is almost 25 percent. Conventional
treatment involves benzodiazepine drugs, which can have serious
side effects, including dependence, daytime drowsiness, and memory
impairment, among others. Kava, on the other hand, has demonstrated
a remarkable safety profile, with side effects of only 1.5 to
2.3 percent reported in studies of more than 3,000 patients. The
adverse events reported most often by kava users were gastrointestinal
complaints, allergic skin reactions, headache, and photosensitivity.
The researchers noted that as patients often prefer natural alternatives,
physicians should consider kava extract as a viable treatment
option for patients experiencing anxiety disorders.
- Rob McCaleb, Herb Research Foundation
[Pittler MH, Ernst E. Efficacy of kava extract for treating
anxiety: systematic review and meta-analysis. J Clin Psychopharmacol
2000; 20: 84-89. Volz H-P, Kieser M. Kava-kava extract WS1490
versus placebo in anxiety disorders: a randomized placebo-controlled
25-week outpatient trial. Pharmacopsychiatry 1997; 30:
1-5.]
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