Does Kava Work for Anxiety? Early Trials Were Positive, the Largest One Was Not
Older pooled trials found kava lowered anxiety scores, but a 16-week, 171-person trial in generalized anxiety disorder found no benefit and more abnormal liver tests. Rare but severe liver injury, and sedative and alcohol interactions, are the main safety issues.
By Kymata Health Editorial Published Last checked
What this article covers
1 evidence profileKey takeaways
From 8 sources- A 2003 Cochrane review pooled 6 trials (345 people) and found kava lowered Hamilton Anxiety scores by 5.0 points more than placebo1.
- A 6-week trial of 58 people with generalized anxiety disorder (GAD) was positive (26% vs 6% remitted), but the follow-up 16-week trial of 171 people found no benefit (17.4% vs 23.8%)24.
- Both GAD trials were co-funded by Integria Healthcare, which makes kava products, alongside Australia's national research council35.
- In the longer trial, memory problems, tremor and abnormal liver tests were more common on kava, though no one met criteria for herb-induced liver injury4.
- Kava has been linked to rare cases of serious or fatal liver injury, and NCCIH says not to combine it with alcohol, benzodiazepines or other sedatives67.
The evidence, graded
Pulled from the trial tables in our evidence profiles. Grades follow our evidence-grading policy.
Graded findings
3 rows- BGrade BAnxiety symptoms (Hamilton Anxiety scale)Improved In 6 trials (345 people) the Hamilton Anxiety score fell 5.0 points more with kava than placebo; adverse events in the trials were mild, transient and infrequent.Kava · Meta-analysis · n=645 · 2003 · PMID 12535473
- CGrade CGeneralized anxiety disorder (6 weeks)Improved Anxiety fell more with kava than placebo (effect size 0.62); 26% versus 6% remitted. More headaches on kava; liver tests did not differ.Kava · RCT · n=58 · 2013 · PMID 23635869
- ∅No effectGeneralized anxiety disorder (16 weeks)No effect No significant difference from placebo (difference of 1.37 points favouring placebo); 17.4% remitted on kava versus 23.8% on placebo. Memory problems, tremor and abnormal liver tests were more frequent on kava, though no one met criteria for herb-induced liver injury.Kava · RCT · n=171 · 2020 · PMID 31813230
Where these trials agree: Kava and anxiety, counted row by row in the Consensus finder.
The short answer
NCCIH says kava supplements may help anxiety but may need several weeks to work, and that kava does not appear helpful for generalized anxiety disorder6. The most rigorous recent trial is negative, so the older positive results deserve caution4.
The liver question is real but rare: NCCIH describes cases of liver injury, some serious or fatal, with both extracts and water-based drinks6.
What the older trials showed
The 2003 Cochrane review found 11 double-blind trials with 645 participants1. In the 6 trials that used the Hamilton Anxiety scale, kava reduced scores more than placebo (weighted mean difference 5.0, 95% CI 1.1 to 8.8)1. Side effects in those trials were mild, transient and infrequent, and the review judged kava relatively safe for short-term use of 1 to 24 weeks while calling for long-term safety data1. Its searches ended in August 20021.
The two generalized anxiety disorder trials
In a 6-week Australian trial, 75 people with GAD enrolled and 58 were analysed after a placebo run-in; they took an aqueous kava extract with 120 to 240 mg of kavalactones a day or placebo2. Anxiety fell more on kava (P = 0.046, effect size 0.62), and 26% vs 6% were in remission by the end2. Headaches were more common on kava, and liver tests did not differ2. The study was funded by the National Health and Medical Research Council and Integria Healthcare, which makes MediHerb and Thompson's kava products3.
The same group then ran a larger phase III trial: 171 unmedicated adults with GAD took 120 mg of kavalactones twice a day or placebo for 16 weeks4. There was no significant difference, with a 1.37-point edge favouring placebo (p = 0.25), and remission was 17.4% on kava vs 23.8% on placebo4. Poorer memory (36 vs 23) and tremor or shakiness (36 vs 23) were more frequent on kava, as were abnormal liver function tests4. The trial was funded by the national research council and co-funded by Integria Healthcare, which the authors say had no role in design or analysis; the lead author disclosed payments from several companies that sell kava5.
The liver story
By late 2002, health agencies had reports from Germany, Switzerland and the US of 11 kava users who developed liver failure and needed transplants, and the FDA issued a consumer advisory on March 25, 20027. A 2010 clinical review of 14 well-documented cases found kava causality highly probable in 1 and probable in 4, with overdose, prolonged use and other medicines or supplements as common risk factors8. The review also pointed to poor-quality kava raw material as a likely contributor8.
NCCIH lists other suggested causes, including unsuitable plant varieties or parts, use with alcohol, contamination, genetic differences, and large or prolonged intake6.
Who should be careful
NCCIH says kava can cause digestive upset, headache and dizziness, and long-term high doses can cause kava dermopathy, a dry, scaly skin condition with temporary yellowing of skin, hair and nails6. These groups face the most risk:
- Anyone drinking alcohol or taking benzodiazepines or other sedatives: NCCIH says kava should not be combined with them6.
- People taking any prescription medicine: NCCIH advises talking with your health care provider first, and the liver-case review found other medicines and supplements were a common risk factor68.
- People with liver disease or liver problems: kava products have been linked to liver failure serious enough to need transplants7.
- Long-term or high-dose users: overdose and prolonged use were risk factors in the assessed liver cases8.
- Pregnancy and breastfeeding: NCCIH says kava may carry special risks because of harmful pyrone constituents6.
- People with diagnosed generalized anxiety disorder: the largest trial found no benefit, so this needs a clinician4.
Quick answers
Common questions
4 answersIs kava tea safer than kava pills?
Not clearly. NCCIH says liver injury cases have involved alcohol or acetone extracts and also water-prepared kava beverages6.
Can I drink alcohol with kava?
NCCIH says kava should not be used together with alcohol or other sedating substances6.
How long does kava take to work?
NCCIH says kava may need to be taken for several weeks to produce an effect6.
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References
8 sources. Numbers in the text link here.
Sources cited in this article
8 sources- 1Kava extract for treating anxietyCochrane Database Syst Rev, 2003 · PMID 12535473
- 2Kava in the treatment of generalized anxiety disorder: a double-blind, randomized, placebo-controlled studyJ Clin Psychopharmacol, 2013 · PMID 23635869
- 3World first clinical trial supports use of Kava to treat anxiety (University of Melbourne release; funding statement)ScienceDaily, 2013
- 4Kava for generalised anxiety disorder: A 16-week double-blind, randomised, placebo-controlled studyAust N Z J Psychiatry, 2020 · PMID 31813230
- 5Kava for generalised anxiety disorder: A 16-week double-blind, randomised, placebo-controlled study (funding and conflict-of-interest statements)Monash University research repository, 2020
- 6Kava: Usefulness and Safety (last updated April 2025)National Center for Complementary and Integrative Health (NCCIH), 2025
- 7Hepatic toxicity possibly associated with kava-containing products--United States, Germany, and Switzerland, 1999-2002MMWR Morb Mortal Wkly Rep, 2002 · PMID 12500906
- 8Kava hepatotoxicity--a clinical reviewAnn Hepatol, 2010 · PMID 20720265
Kava and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. This page has no product or affiliate links.