Friday, June 12, 2009


Kava is a perennial shrub native to islands of the South Pacific. It has been ingested there as part of local culture. It has a relaxing effect.

Kava has been associated with liver toxicity: there have been cases of liver failure necessitating liver transplant, and there have been fatalities. As a result, the sale of kava is restricted in Canada.

Here is a reference about the liver toxicity issue:

In this 2008 article from a liver disease journal, cases of kava toxicity are reviewed. It is concluded that liver damage is a rare side effect of kava. It also found that many of those experiencing liver toxicity had used higher doses of kava, for longer periods of time, than recommended.


Here is a 2009 prospective, randomized, controlled study from Australia, in which 3 weeks of kava treatment (250 mg kava lactones per day) had minimal side-effects and led to substantial, clinically significant improvements compared to placebo in generalized anxiety symptoms and depressive symptoms:
As a critical commentary here, I think that 3 weeks is a VERY short study period, and therefore has limited clinical relevance. A great many approaches can relieve anxiety over a brief period of time (e.g. benzodiazepines); it's of much greater interest to see what happens after 3 months, or after 3 years!

Here is a 2003 Cochrane review, showing significant benefits in anxiety symptoms from kava treatment:

Here is a negative study from 2005, which showed that neither valerian nor kava differed from placebo in relieving anxiety or insomnia. The study participants were recruited on the internet, and were sent the blinded medication or placebo through the mail (another example of an interesting new study design):

In conclusion, kava seems promising as a treatment for anxiety. But there appears to be a small risk of very dangerous liver toxicity. It will require ongoing study to clarify risks vs. benefits, or to discover ways to minimize the risk of liver damage.

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