Kava
Piper methysticum
Genuinely calming for anxiety — with a real liver caveat.
Moderate evidence
🌙Sleep & Mood
Evidence tier
Moderate
Research weight
Citations
14 verified / 14
Classification
Sleep & Mood
❝
What the evidence says. Several controlled trials; effects real but modest or context-dependent.
⚠
Health warning. Kava is effective short-term for anxiety but is linked to rare liver injury. Avoid alcohol and other medications, limit to short courses (≤8 weeks), and stop immediately if you notice signs of liver trouble.
What is Kava?
Kava (Piper methysticum) is a sleep and mood supplement used for reduced anxiety (short-term). NutriDex grades the human evidence as Moderate. Kava is a Pacific Island plant whose kavalactones have a real, evidence-backed calming effect. Systematic reviews find kava outperforms placebo for short-term anxiety, though the effect is small and the best-powered generalized-anxiety-disorder trial (Sarris 2013) was negative. Its reputation was damaged by reports of liver injury; the risk appears rare and linked to prolonged use, poor-quality products, alcohol and drug interactions, but idiosyncratic hepatotoxicity cannot be excluded even with traditional preparations. Quality and duration matter greatly.
Purported Benefits
✓Reduced anxiety (short-term)
✓Relaxation without heavy sedation
Dosing & Compounds
Typical Dose
Standardized extracts ~120–280 mg kavalactones/day, short-term (≤8 weeks).
Active Compounds
Safety & Cautions
⚠ Rare but serious liver injury. Avoid with alcohol, liver disease, or hepatotoxic drugs; do not combine with sedatives; limit duration. Can cause drowsiness — don't drive after use. Educational only — always check with your doctor or pharmacist before combining Kava with any medicine.
Kava drug interactions
Known or theoretical interactions between Kava and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Kava with any medicine.
Avoid
Benzodiazepines & CNS sedatives
Excessive drowsiness and impaired coordination; a report of coma with alprazolam.
Kava has CNS-depressant (GABAergic) activity that deepens sedation from sedative drugs. NCCIH — Kava
Avoid
Alcohol & liver-stressing drugs
Increased risk of serious liver injury; kava itself is linked to hepatotoxicity.
Kava is associated with liver damage; combining with alcohol/hepatotoxic drugs compounds hepatic stress. NCCIH — Kava
Key Studies ★ 14 studies
Systematic review
Smith 2018 (systematic review)
✓ PubMed
Kava outperformed placebo for anxiety in several short-term RCTs.
Meta-analysis
Ooi 2018
✓ PubMed
Systematic review and meta-analysis specific to GAD (12 articles). Meta-analysis of three placebo-controlled trials (n=130) favoured Kava with effect sizes between 0.59 and 0.99 (standardised mean difference) but WITHOUT reaching statistical significance. Concluded current evidence is promising but insufficient to confirm efficacy beyond placebo; Kava judged safe/well tolerated short-term (4-8 weeks) at 120-280 mg/day kavalactones.
Systematic review
Baric/Trkulja 2018
✓ PubMed
Systematic review and network meta-analysis of CAM for GAD (32 RCTs). Direct Kava-vs-placebo comparisons (4 trials, n=233) were highly heterogeneous; network meta-regression suggested only a modest, non-significant Kava effect (end-of-treatment HAM-A difference -3.24 points; 95% CI -6.65 to 0.17; p=0.059). Reinforces marginal/uncertain efficacy signal.
Meta-analysis
Pittler & Ernst 2000
✓ PubMed
Systematic review and meta-analysis of double-blind placebo-controlled RCTs of oral Kava extract for anxiety. All seven reviewed trials favoured Kava; meta-analysis of three trials showed a significant reduction in Hamilton Anxiety Rating Scale total score favouring Kava (weighted mean difference 9.69 points; 95% CI 3.54-15.83). Landmark early evidence that Kava is superior to placebo for symptomatic anxiety.
rct
Savage 2023 (neuroimaging RCT, Nutrients)
✓ PubMed
In a randomized placebo-controlled neuroimaging sub-study (n=37), kava significantly reduced dorsal anterior cingulate cortex GABA at 8 weeks (p=0.049), indicating central GABAergic modulation independent of symptom change.
rct
Sarris 2023 (gene-expression post hoc RCT analysis)
✓ PubMed
Post hoc analysis of a GAD RCT found kava altered peripheral gene expression versus placebo, supporting a biological mechanism though without clear clinical anxiolytic benefit.
rct
Sarris 2020 (K-GAD RCT, Aust N Z J Psychiatry)
✓ PubMed
In the largest GAD trial (n=171, 16 weeks), aqueous noble kava (240 mg kavalactones/day) showed no significant anxiety reduction versus placebo, with remission actually lower in the kava arm (17.4% vs 23.8%).
rct
Leitzman 2020 (kava smokers pilot trial, Cancer Prev Res)
✓ PubMed
In a pilot trial of active smokers, a 7-day course of kava increased urinary excretion of the tobacco carcinogen metabolite total NNAL and reduced 3-methyladenine and total nicotine equivalents, suggesting enhanced NNK detoxification and a potential lung-cancer chemoprevention/cessation effect.
guideline
NCCIH (NIH) — Kava: Usefulness and Safety
✓ Source
NIH's NCCIH states kava supplements may help anxiety but do not appear effective for generalized anxiety disorder, and warns that various kava products have been linked to rare cases of liver injury, some serious or fatal.
RCT
Sarris (KADSS) 2009
✓ PubMed
First clinical trial of an aqueous Kava extract: 3-week double-blind, placebo-controlled crossover trial (n=60, 250 mg kavalactones/day) in generalised anxiety. Kava produced a highly significant pooled reduction in Hamilton Anxiety Scale vs placebo (p<0.0001) with a large effect size (d=2.24), plus significant reductions in Beck Anxiety Inventory and MADRS depression scores; no clinical hepatotoxicity. Landmark positive RCT supporting short-term aqueous Kava.
review
Wang 2021 (review, Evid Based Complement Alternat Med)
✓ Full text
Structure-activity review concluding that flavokawain B, rather than the psychoactive kavalactones, is the constituent most implicated in kava hepatotoxicity, alongside poor raw-material quality and prolonged use.
Safety / toxicology
LiverTox / hepatotoxicity reviews
✓ Full text
Rare but real liver injury; risk rises with long use, alcohol and co-medication.
systematic_review
Pittler & Ernst 2003 (Cochrane systematic review)
✓ PubMed
Cochrane meta-analysis of 6 placebo-controlled RCTs (345 participants) found kava extract significantly reduced Hamilton Anxiety Scale scores versus placebo (weighted mean difference 5.0 points, 95% CI 1.1-8.8; p=0.01), supporting a small short-term anxiolytic effect.
Study
Traditional use
✓ Full text
Pacific Island use shows low liver harm — product quality is key.