Kava
A Cochrane review of short trials found lower anxiety scores than placebo. A 16-week trial in 171 people with generalized anxiety disorder found no difference and more liver test abnormalities. Eleven people in the US and Europe needed liver transplants after kava products. The FDA issued a 2002 advisory, and several countries restricted sales.
Add to Bio HackChecked 2026-11-09
- Status
- Dietary supplement in the US. In March 2002 the FDA issued a consumer advisory that kava products may be associated with severe liver injury.
- Also called
- Piper methysticum, kava kava, kawa, kavalactones, kavapyrones, kavain, WS 1490, LI 150, awa, yaqona
- Taken for
- anxiety, stress, relaxation, sleep, insomnia, social ease, mood
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help0
No benefit shown in research yet.
Reported risks4
- ModerateCase reports: liver failure and transplants in 11 kava users by 2002, including a 14-year-old girl. Most likely cases exceeded dose or duration limits.How often is not known
- ModerateFDA issued a 2002 advisory on the potential risk of severe liver injury with kava, and five other countries restricted kava sales.How often is not known
- LimitedLimited evidence: liver test abnormalities were more frequent on kava in one trial, and community kava use was linked to higher liver enzymes.How often is not known
- LimitedOne trial found poorer memory and tremor were each reported by 36 people on kava against 23 on placebo.How often is not known
What people take it for, and what was found
Mixed results3
Anxiety symptoms
Mixed results: a Cochrane review found anxiety scores fell 5 points more than placebo, while a later 4-week trial found no added drop.
The numbers and sources
- Effect
- In 11 trials (645 participants), 6 studies pooled on the Hamilton Anxiety scale showed a 5.0-point greater reduction with kava extract than placebo (95% CI 1.1 to 8.8, n 345) [1]. In an internet-based trial of 391 adults with anxiety and insomnia, anxiety scores fell 14.4 points on placebo, and the drop on kava was 2.7 points smaller (95% CI -0.8 to 6.2) [2].
- Population
- Adults with anxiety in trials of 1 to 24 weeks [1]. 391 US adults over 4 weeks [2].
- Sources
- [1], [2]
- Caveats
- The Cochrane trials were short, and the review sought data from kava manufacturers [1]. The two sources differ in direction.
Generalized anxiety disorder
Small trials found mixed results: a 6-week trial found less anxiety than placebo, and a larger 16-week trial found no difference.
The numbers and sources
- Effect
- In 58 analyzed participants with generalized anxiety disorder, 6 weeks of an aqueous extract (120 to 240 mg kavalactones a day) lowered anxiety more than placebo (Cohen d 0.62), and 26% against 6% were in remission [3]. In a 16-week phase III trial of 171 people with the same diagnosis, 120 mg of kavalactones twice a day did not differ from placebo (1.37 points favoring placebo, p 0.25), and remission was 17.4% on kava and 23.8% on placebo [4].
- Population
- Adults with generalized anxiety disorder in Australia [3][4].
- Sources
- [3], [4]
- Caveats
- The two trials, from the same research group, disagree. The larger, longer trial was funded by Australia's National Health and Medical Research Council [4].
Sleep
Mixed results: one trial found better sleep quality on kava in people with anxiety-related sleep problems, while a larger internet trial found no relief of insomnia over placebo.
The numbers and sources
- Effect
- In 61 patients with sleep disturbances tied to anxiety, 200 mg a day of kava extract WS 1490 for 4 weeks improved self-rated sleep quality (p = 0.007) and feeling rested after sleep (p = 0.018) more than placebo, with no drug-related adverse events [8]. In 391 adults with anxiety and insomnia recruited online, neither kava nor valerian relieved anxiety or insomnia more than placebo over 28 days [2].
- Population
- 61 patients with anxiety-related sleep disturbances in a multicenter trial [8]. 391 adults with anxiety and insomnia in the US [2].
- Sources
- [8], [2]
- Caveats
- Both trials lasted 4 weeks and measured sleep by questionnaire. In the larger trial, the primary sleep comparison was for valerian, and the placebo group improved by 8.3 points on the insomnia index [2].
Doses studied
The 6-week trial used 120 to 240 mg of kavalactones a day [3], and the 16-week trial 120 mg twice a day [4]. In the European liver transplant cases, products were taken at 60 to 240 mg a day for 8 weeks to 12 months [5]. A German causality review used a regulatory limit of 120 mg kavapyrones a day for no more than 3 months as its reference [6].
Risks
Reported risks4
Liver failure and transplants
Case reports: liver failure and transplants in 11 kava users by 2002, including a 14-year-old girl. Most likely cases exceeded dose or duration limits.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- By 2002, 11 people in Germany, Switzerland and the US who used kava products had liver failure and liver transplants. The two US cases were a 45-year-old woman after about 8 weeks of use and a 14-year-old girl, both previously healthy [5]. A causality analysis of 26 cases suspected by regulators found 8 with some degree of causality for kava with or without other drugs. In 6 of these, kava was taken above the regulatory dose or for longer than the regulatory duration. One patient who followed the dose and duration limits had probable kava liver injury [6].
- Population
- Case reports to US and European regulators [5][6].
- Sources
- [5], [6]
- Caveats
- Case reports cannot give a rate. The CDC report notes FDA research suggesting fewer than 1% of severe supplement adverse events are reported to the FDA [5]. Most European cases involved ethanol or acetone extracts [5].
Regulator actions
FDA issued a 2002 advisory on the potential risk of severe liver injury with kava, and five other countries restricted kava sales.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- On March 25, 2002, the FDA issued a consumer advisory on the potential risk of severe liver injury with kava products, in response to five case reports. Germany, Switzerland, Canada, Australia and France restricted the sale of kava products, citing liver adverse events and documented liver toxicity after re-exposure [5].
- Population
- Consumers in the named countries [5].
- Sources
- [5]
- Caveats
- These actions date from 2002, as reported by the CDC [5]. Later changes to these restrictions were not checked for this page.
Liver test changes in trials and traditional use
Limited evidence: liver test abnormalities were more frequent on kava in one trial, and community kava use was linked to higher liver enzymes.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- In the 16-week trial, liver function test abnormalities were more frequent on kava than placebo, though no participant met criteria for herb-induced liver injury [4]. In 98 Indigenous Australians, recent use of aqueous kava, averaging 118 g of powder a week, was linked to higher GGT and alkaline phosphatase, which began returning to baseline after 1 to 2 weeks without kava. ALT and bilirubin were not elevated [7]. In the 6-week trial, liver tests did not differ from placebo [3].
- Population
- 171 trial participants [4]. A cross-sectional study of 98 people in one Arnhem Land community [7]. 58 trial participants [3].
- Sources
- [4], [7], [3]
- Caveats
- The community study was cross-sectional and could not follow individuals over time [7].
Memory problems and tremor
One trial found poorer memory and tremor were each reported by 36 people on kava against 23 on placebo.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- In the 16-week trial, poorer memory and tremor or shakiness were each reported by 36 participants on kava and 23 on placebo [4]. In the 6-week trial, headaches were more frequent on kava [3].
- Population
- 171 [4] and 58 [3] adults with generalized anxiety disorder.
- Sources
- [4], [3]
- Caveats
- Counts come from two trials.
Claims tested and not found
Sources
- Pittler MH, Ernst E. Kava extract versus placebo for treating anxiety. Cochrane Database of Systematic Reviews. 2003. https://doi.org/10.1002/14651858.CD003383
- Jacobs BP, Bent S, Tice JA, et al. An Internet-Based Randomized, Placebo-Controlled Trial of Kava and Valerian for Anxiety and Insomnia. Medicine. 2005. https://doi.org/10.1097/01.md.0000172299.72364.95
- Sarris J, Stough C, Bousman CA, et al. Kava in the Treatment of Generalized Anxiety Disorder: A Double-Blind, Randomized, Placebo-Controlled Study. Journal of Clinical Psychopharmacology. 2013. https://doi.org/10.1097/JCP.0b013e318291be67
- Sarris J, Byrne GJ, Bousman CA, et al. Kava for generalised anxiety disorder: A 16-week double-blind, randomised, placebo-controlled study. Australian & New Zealand Journal of Psychiatry. 2020. https://doi.org/10.1177/0004867419891246
- Centers for Disease Control and Prevention. Hepatic Toxicity Possibly Associated with Kava-Containing Products, United States, Germany, and Switzerland, 1999 to 2002. Morbidity and Mortality Weekly Report. 2002. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5147a1.htm
- Teschke R, Schwarzenboeck A, Hennermann KH. Kava hepatotoxicity: a clinical survey and critical analysis of 26 suspected cases. European Journal of Gastroenterology & Hepatology. 2008. https://doi.org/10.1097/MEG.0b013e3283036768
- Clough AR, Bailie RS, Currie B. Liver Function Test Abnormalities in Users of Aqueous Kava Extracts. Journal of Toxicology: Clinical Toxicology. 2003. https://doi.org/10.1081/CLT-120025347
- 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. Journal of Affective Disorders. 2004. https://doi.org/10.1016/s0165-0327(02)00238-0