GradedHealth

Kava

Last reviewed October 2026 · Based on 26 studies

Bottom line

Kava may ease anxiety for a few weeks: several short trials favored it over placebo, but the largest recent trial found no benefit. Liver injury has been reported in people who use kava, so liver and drug safety are the main caveats.

What it helps with

  • Eases anxiety — Mixed results, evidence grade C (Limited). Several RCTs and two pooled reviews; downgraded for inconsistency (largest recent RCT negative) and small total sample.
  • Harms the liver — Harm, evidence grade C (Limited). Mainly case reports and a review of cases, plus short trials that mostly found no change; no pooled risk estimate.
  • Interacts with other medicines — Harm, evidence grade C (Limited). Small enzyme study in 12 people plus reports of interactions; no outcome data; surrogate measure.

What it is

Kava (Piper methysticum) is a plant from the South Pacific whose root is made into drinks, capsules and tonics. Its calming effects come from compounds called kavalactones [1].

How it might work

Proposed, not yet confirmed: kavalactones may act on GABA receptors and on noradrenaline and MAO-B in the brain [1]. A brain-scan study of 37 people found kava lowered GABA in one brain area [2]. A post hoc gene study found changes in two genes linked to GABA and catecholamine pathways, which did not hold up after statistical correction [3].

What the research says

A 2018 review found kava beat placebo in 3 of 7 placebo-controlled trials. Five trials with 330 people gave a pooled risk ratio of 1.50 (95% CI 1.12 to 2.01) for people who responded [4]. Three placebo-controlled trials with 130 people gave effect sizes of 0.59 to 0.99 in favor of kava, not statistically significant [5]. A 2018 network analysis estimated a Hamilton anxiety score difference of about 3.2 points, not statistically significant [6]. A 2022 network analysis of 29 herb trials found kava lowered anxiety scores by about 2.5 points, while its authors said kava may not work in generalized anxiety disorder specifically [7]. Individual trials are mixed: a 2013 trial of 58 adults found kava beat placebo (remission 26% vs 6%) [8]; a 2020 trial of 171 adults over 16 weeks found no significant difference (remission 17% vs 24%) [9]; a 4-week trial of 37 people found no difference [10]; and a 2003 trial of 127 people found LI 150 extract as effective as buspirone and opipramol, with no placebo group [11]. A single dose did not reduce anxiety in a crossover trial of 22 adults [12]. An earlier 2010 review found the evidence strong but could not pool results because the trials were few and varied [13].

Doses used in studies

Trials used standardized extracts giving about 120 to 280 mg of kavalactones a day [5][8]. A 16-week trial used 120 mg twice a day [9]. LI 150 was given at 400 mg a day for 8 weeks [11]. One crossover trial tested a single 180 mg dose [12]. These are trial doses, not recommendations.

Safety and interactions

Side effects: in a 16-week trial, poorer memory and tremor were more common on kava than placebo [9]; headaches were more common in a 6-week trial [8]. Otherwise adverse events were similar to placebo in a 2018 review [4]. Upper limit: the studies read did not set one; trials used up to 280 mg of kavalactones a day for up to 16 weeks [5][9]. Liver: kava is among the herbs most often linked to liver injury in case reports; a review counted 936 cases across all herbs, with liver transplant needed in 6.6% [14]. Trial liver tests were mostly unchanged, but abnormal tests were more frequent on kava in a 16-week trial, with no herb-induced liver injury [9][15]. Liver toxicity is especially possible with use beyond 8 weeks [4]. Medicines: kava lowered CYP2E1 enzyme activity by about 40% in 12 healthy people over 28 days [16]; possible interactions are reported with alprazolam, levodopa, paroxetine [17] and benzodiazepines [18]. Heavy long-term use can cause a scaly skin condition, kava dermopathy, which fades after stopping [1]. Withdrawal after heavy use can be severe; one emergency case needed phenobarbital [19]. Pregnancy and breastfeeding: no controlled studies were found. One case report describes a mother using a kava and kratom product through pregnancy and a newborn with a similar skin rash [20]. Kidney disease and bleeding disorders or blood thinners: the searches found no studies on kava in these groups.

Caveats and open questions

Results conflict across trials, and most trials are small and short; none of the trials read ran longer than 16 weeks [9][4]. Trials used specific extracts, so results may not carry over to other products [8]. One author of a brain-scan study reports payments from a kava product maker [2]. A recruiting trial of a branded kava tonic measures stress in healthy adults (see trial IDs).

References

  1. Therapeutic potential of kava in the treatment of anxiety disorders.. CNS Drugs, 2002.
  2. Neuroimaging Insights: Kava's (Piper methysticum) Effect on Dorsal Anterior Cingulate Cortex GABA in Generalized Anxiety Disorder.. Nutrients, 2023.
  3. Effect of kava (Piper methysticum) on peripheral gene expression among individuals with generalized anxiety disorder: A post hoc analysis of a randomized controlled trial.. Phytother Res, 2023.
  4. The effectiveness and safety of Kava Kava for treating anxiety symptoms: A systematic review and analysis of randomized clinical trials.. Complement Ther Clin Pract, 2018.
  5. Kava for Generalized Anxiety Disorder: A Review of Current Evidence.. J Altern Complement Med, 2018.
  6. Complementary and Alternative Medicine Treatments for Generalized Anxiety Disorder: Systematic Review and Meta-analysis of Randomized Controlled Trials.. Adv Ther, 2018.
  7. Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis.. Pharmacol Res, 2022.
  8. Kava in the treatment of generalized anxiety disorder: a double-blind, randomized, placebo-controlled study.. J Clin Psychopharmacol, 2013.
  9. Kava for generalised anxiety disorder: A 16-week double-blind, randomised, placebo-controlled study.. Aust N Z J Psychiatry, 2020.
  10. A placebo-controlled study of Kava kava in generalized anxiety disorder.. Int Clin Psychopharmacol, 2002.
  11. Kava-Kava extract LI 150 is as effective as Opipramol and Buspirone in Generalised Anxiety Disorder--an 8-week randomized, double-blind multi-centre clinical trial in 129 out-patients.. Phytomedicine, 2003.
  12. The acute effects of kava and oxazepam on anxiety, mood, neurocognition; and genetic correlates: a randomized, placebo-controlled, double-blind study.. Hum Psychopharmacol, 2012.
  13. Nutritional and herbal supplements for anxiety and anxiety-related disorders: systematic review.. Nutr J, 2010.
  14. Herb-induced liver injury: Systematic review and meta-analysis.. World J Clin Cases, 2021.
  15. Kava for the treatment of generalized anxiety disorder RCT: analysis of adverse reactions, liver function, addiction, and sexual effects.. Phytother Res, 2013.
  16. In vivo effects of goldenseal, kava kava, black cohosh, and valerian on human cytochrome P450 1A2, 2D6, 2E1, and 3A4/5 phenotypes.. Clin Pharmacol Ther, 2005.
  17. Interactions between herbal medicines and prescribed drugs: an updated systematic review.. Drugs, 2009.
  18. A systematic review of the safety of kava extract in the treatment of anxiety.. Drug Saf, 2002.
  19. Severe kava withdrawal managed with phenobarbital.. Am J Emerg Med, 2025.
  20. Neonatal and Maternal Ichthyosiform Dermopathy in Association with Kava Use during Pregnancy.. J Med Toxicol, 2024.