Lehrl S. Clinical efficacy of kava extract WS 1490 in sleep disturbances associated with anxiety disorders. Results of a multicenter, randomized, placebo-controlled, double-blind clinical trial. J Affect Disord. 2004 Feb;78(2):101-10.
A multicenter, randomized, double-blind clinical study of Kava special extract WS 1490 and its use in sleep disturbances associated with anxiety. 61 patients participated in the trial. Patients were given either 200 mg WS 1490 kava extract or placebo daily over a period of four weeks. Patients were scored on the Hamilton Anxiety Rating Scale (HAMA). Improvement in scores for 'quality of sleep' and 'recuperative effect after sleep' for patients after completing treatment with kava was statistically significant compared with those receiving placebo. No drug-related adverse effects were noted. A full quarter of patients did not comply with study protocol.
Jacobs B, et al. An Internet-Based Randomized, Placebo-Controlled Trial of Kava and Valerian for Anxiety and Insomnia. Medicine 2005 Jul;84(4):197-207.
An Internet-based double-blind study found that kava is no more effective than an placebo for anxiety. 391 patients were recruited through e-mail or advertisements on web sites. The participants were randomly assigned to 1 of 3 treatment groups that were given capsules containing either kava, valerian, or a placebo for 4 weeks. At the end of the study, patients who received kava or valerian had similar improvements in anxiety symptoms and in sleep as compared to the placebo group. Kava group and the placebo group reported similar adverse events with no report on hepatotoxicity.
Brown AC, et al. Traditional kava beverage consumption and liver function tests in a predominantly Tongan population in Hawaii. Clin Toxicol (Phila). Jun-Aug 2007;45(5):549-556.
To determine if chronic kava beverage consumption may result in hepatotoxicity, liver functional analysis was carried out in 31 healthy, adult kava drinkers and 31 healthy, adult non-kava drinkers. Liver enzymes including aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and gamma-glutamyl transpeptidase (GGT) as well as total bilirubin, direct bilirubin, indirect bilirubin, and albumin were determined. Individuals regularly consuming kava beverage were more likely to have elevated GGT levels. Further studies are required to determine if GGT levels can be reduced upon abstaining from kava drinking. In addition, determining whether elevated GGT levels mediate kava-induced hepatotoxicity is necessary.