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Kava extract reduces anxiety

Clinical bottom line: Kava extract 300 mg daily is an effective treatment for anxiety syndrome in nonpsychotic patients. Included studies were of good methodological quality, but the analyses were based on few patients.

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Anxiety disorders are common with 1 year prevalence rates of about 17% and a lifetime prevalence of 25% according to American data. Use of alternative therapies for anxiety is common. Uncontrolled studies show kava extract to help individuals with anxiety.

Systematic review:

Pittler MH, Ernst E. Efficacy of kava extract for treating anxiety: Systematic review and meta-analysis.

Date review completed: June 1998

Number of trials included: 7 total; 3 in the meta-analysis.

Number of patients: (377 total)

Control groups: placebo.

Main outcomes: Hamilton rating scale for anxiety (HAM-A), mean change compared with baseline.

Inclusion criteria were randomised, double blind, placebo controlled trial which assessed the effectiveness of Kava extract for the treatment of anxiety.

Medline, Embase, Biosis. AMED, CICSOM and the Cochrane Library were searched (to June 1998) for published reports. The reviewers' own files were searched for relevant studies. Bibliographies of retrieved reports were checked for additional citations and no language restrictions were made. Manufacturers of kava extract products and experts were contacted for published and unpublished trials. Data were extracted in a standardised, predefined manner by the two reviewers who were blind to the author, journal, institution etc of the trials. Methodological quality was rated using a validated 5-point scale. A meta-analysis was conducted and weighted mean differences, with 95% confidence intervals, were calculated using a random effects model.


Seven studies met the inclusion criteria.


Three trials of good methodological quality provided sufficient information to be included in a meta-analysis. The 198 outpatient or general practice patients had diagnosed, nonpsychotic anxiety syndrome and were roughly 40-60 years of age. Baseline total HAM-A score was greater than 19 in all studies. Kava extract 300 mg daily was compared with placebo over 4, 8 or 24 weeks. All trials showed a significant reduction in the total HAM-A score from baseline with kava extract compared with placebo; the weighted mean difference was 9.7 (3.5 to 16).

Other studies:

The four studies which were not included in the meta-analysis assessed different doses of kava extract (300-800 mg daily) in 179 patients. Two studies assessed patients with diagnosed anxiety syndrome, one assessed preoperative patients and one assessed patients before confirmed diagnosis of anxiety syndrome. All studies showed a significant reduction in anxiety with kava extract compared with placebo.

Adverse effects

Adverse effects were uncommon. Stomach upset, drowsiness, headache, restlessness, tremor and tiredness were reported.



The included studies were of good methodological quality; they were both randomised and double blind, which reduces the possibility of bias, and used placebo control. The meta-analysis shows that kava extract (300 mg daily) is effective in reducing anxiety, though the results were based on only 198 patients. Further trial activity would help verify this finding.

Further reading

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