Supplement analysis backed by scientific evidence · PT

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Moderate evidenceStress & mood

Kava

Older meta-analytic data show kava beats placebo for anxiety, but the largest and best-conducted modern trial was flatly negative — and the drug carries a genuine, regulator-recognised hepatotoxicity signal. The risk-benefit case is much weaker than kava's popularity implies.

What the science says

  • Reduces anxiety symptoms Moderate evidence

    A Cochrane review of 12 double-blind trials found kava extract superior to placebo, with a pooled Hamilton Anxiety Rating Scale advantage of roughly 3.9 points (95% CI 0.1-7.7) — statistically significant but with a confidence interval brushing zero, and drawn mostly from small, short trials.

  • Effective for diagnosed generalised anxiety disorder Limited evidence

    The largest dedicated trial (K-GAD, 171 patients, 16 weeks, 240 mg kavalactones/day of an aqueous extract) found no significant difference from placebo on anxiety outcomes, and reported more liver-enzyme elevations in the kava arm. An earlier, much smaller 6-week trial by the same group had been positive, so the modern data are best described as mixed-to-negative.

  • Acts without the dependence liability of benzodiazepines Limited evidence

    Kavalactones modulate GABA-A allosterically and act on sodium and calcium channels without the classic benzodiazepine binding site, and trials have not reported withdrawal syndromes. However, no long-term controlled study has formally assessed dependence, tolerance or cognitive effects, so this is a mechanistic argument rather than a demonstrated one.

Dosage & safety

Studied doseTrials used 120-280 mg of kavalactones per day, most commonly 240 mg/day, in divided doses for 4-16 weeks. Traditional water-based (aqueous) extracts of noble kava root are preferred; acetone and ethanol extracts and preparations using stems, leaves or peelings are associated with most of the reported liver injury. Kavalactone content is what matters — raw root powder weight tells you little.
SafetyKava carries the most serious safety flag of any common calming herb: dozens of reports of severe hepatotoxicity, including liver failure and transplant, led to bans or restrictions in Germany, Switzerland, France, Canada and the UK, several of which were later modified or reversed. Do not use with alcohol, paracetamol/acetaminophen, statins, methotrexate or any hepatotoxic drug, and avoid entirely with pre-existing liver disease. Kava causes clear driving and psychomotor impairment. Heavy chronic use produces kava dermopathy — a dry, scaly, yellowed rash. It inhibits several CYP enzymes (notably CYP2E1 and CYP1A2), so it can raise levels of co-administered drugs, and can worsen extrapyramidal symptoms in Parkinson's disease. Contraindicated in pregnancy, breastfeeding and depression. Baseline and periodic liver function testing is reasonable if used at all.

Scientific references

Where to buy

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