Design	Description	Comments
Meta-analyses on GAD	A Cochrane systematic review identified 12 RCTs of effects of kava on patients with GAD4; the meta-analysis included seven trials that met quality criteria (n = 380); kava significantly reduced Hamilton Anxiety Scale scores, although the weighted mean difference between kava and placebo was only 3.9 scale points; the other five trials (n = 320) showed similar tendencies; a replication meta-analysis involving only those RCTs that used extract WS1490 replicated and extended these results5	Kava was consistently better than placebo in producing small reductions in anxiety symptoms; side effects noticed across all studies were “mild, transient, and infrequent”4; the authors concluded that kava taken for one to 24 weeks was safe and mildly effective; the replication5 allowed more comparisons between patient subgroups and suggested most improvement effects in women and patients younger than 53 years
RCTs on GAD	Recent small RCTs involving patients with GAD (n = 64) showed no significant effect of kava,6 with treatments typically lasting four weeks	Trial durations were short, and sample size was small; although studies of eight weeks' duration7 have shown effectiveness, a 25-week study8 showed that therapeutic effects started in the eighth week
RCT on safety	Recent examinations of adverse event reports with kava9 and improved understanding of the pharmacologic substances in kava10 show that its safety compares favorably with FDA-approved treatments for anxiety disorders	Researchers concluded that liver toxicity is rare and idiosyncratic, with the majority of reported cases resulting from the combination of kava with other hepatoactive agents; the benefits of kava seem to outweigh its risks10
Case reports on safety	Cases of liver toxicity have been reported, some requiring organ transplants; kava preparations withdrawn from the market in many countries; the FDA issued an advisory11; later, research suggested that nonstandard inclusion of the kava plant's bark in kava preparations increased toxicity level12	Unclear if dosing, preexisting liver damage, or toxic combinations with other hepatoactive agents were causative