Efficacy of Kava Extract for Treating Anxiety: Systematic Review and Meta-Analysis

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Abstract
Synthetic anxiolytic drugs are effective for treating anxiety, but they are burdened with adverse effects. Constraints on resources and time often render therapies such as psychologic interventions impracticable. Thus, an effective oral medication with few adverse effects would be a welcome addition to the therapeutic repertoire. This systematic review and meta-analysis was aimed at assessing the evidence for or against the efficacy of kava extract as a symptomatic treatment for anxiety. Systematic literature searches were performed in the computerized databases MEDLINE, EMBASE, BIOSIS, AMED, CISCOM, and the Cochrane Library (all from their respective inception to June 1998). The search terms used were kava, kawa, kavain, Piper methysticum, and Rauschpfeffer (German term for Piper methysticum). Experts on the subject were contacted to provide further information. There were no restrictions regarding the language of publication. Double-blind, randomized, placebo-controlled trials of oral kava extract for the treatment of anxiety were included. All publications were blinded before assessment by a person not involved in the study. Data were extracted in a standardized, predefined fashion independently by the two reviewers. The methodologic quality of all trials was assessed. Superiority of kava extract over placebo was suggested by all seven reviewed trials. The meta-analysis of three trials suggests a significant difference in the reduction of the total score on the Hamilton Rating Scale for Anxiety in favor of kava extract (weighted mean difference, 9.69; 95% confidence interval, 3.54-15.83). These data imply that kava extract is superior to placebo as a symptomatic treatment for anxiety. Therefore, kava extract is an herbal treatment option for anxiety that is worthy of consideration.