Herbs & Supplements:
Kava
Piper methysticum

Principal Proposed Uses
  • Anxiety, Insomnia
Other Proposed Uses
  • Alcohol Withdrawal, Tension Headaches

Kava is a member of the pepper family that has long been cultivated by Pacific Islanders for use as a social and ceremonial drink. The first description of kava came to the West from Captain James Cook on his celebrated voyages through the South Seas. Cook reported that on occasions when village elders and chieftains gathered together for significant meetings, they would hold an elaborate kava ceremony at the beginning to break the ice (not that there's much ice out there). Typically, each participant would drink two or three bowls of chewed-up kava mixed with coconut milk. Kava was also drunk in less formal social settings as a mild intoxicant.

When they learned about kava's effects, European scientists set to work trying to isolate its active ingredients. However, it wasn't until 1966 that substances named kavalactones were isolated and found to be effective sedatives. One of the most active of these is dihydrokavain, which has been found to produce a sedative, painkilling, and anticonvulsant effect.^1,2,3 Other named kavalactones include kavain, methysticin, and dihydromethysticin.

High dosages of kava extracts cause muscular relaxation, and at very high dosages paralysis without loss of consciousness develops.^4–7 Kava is also a local anesthetic, producing peculiar numbing sensations when held in the mouth.

The method of action of kava is not fully understood. Conventional tranquilizers in the Valium family interact with special binding sites in the brain called GABA receptors. Early studies of kava suggested that the herb does not affect these receptors.⁸ However, more recent studies have found an interaction.^9,10 The early researchers may have missed the connection because kava appears to affect somewhat unusual parts of the brain.

NOTE: Recent case reports of liver damage have raised significant safety concerns about the use of kava.  See Safety Issues below.

What Is Kava Used for Today?

In the words of Germany's Commission E, kava is useful for relieving "states of nervous anxiety, tension, and agitation."

Warning:Various medical conditions, such as hyperthyroidism, can produce symptoms similar to anxiety. Medical evaluation is strongly recommended before self-treating with kava.

There is some evidence that kava can help insomnia.^11,12 One animal study suggests that kava may have value as an aid to alcohol withdrawal.³⁵ Kava has also been proposed as a treatment for tension headaches.

Contrary to many reports in the media, there is no evidence that kava actually improves mental function. Two studies are commonly cited as if to prove this, but actually there was only one study performed: It was simply described in two separate articles.^29,30 This tiny study found that kava does not impair mental function but doesn't show that kava improves it. A slight improvement was seen on a couple of tests, but it was statistically insignificant (too small to mean anything).

What Is the Scientific Evidence for Kava?

There have been six meaningful studies of kava, involving a total of more than 400 participants. The best of these was a 6-month, double-blind study that tested kava's effectiveness in 100 people with various forms of anxiety.^1316,18,38 Over the course of the trial, they were evaluated with a list of questions called the Hamilton Anxiety Scale (HAM-A). The HAM-A assigns a total score based on such symptoms as restlessness, nervousness, heart palpitations, stomach discomfort, dizziness, and chest pain. Lower scores indicate reduced anxiety. Participants who were given kava showed significantly improved scores beginning at 8 weeks and continuing throughout the duration of the treatment.

This study is notable for the long delay before kava was effective. Previous studies had shown a good response in 1 week.^14,15,16 The reason for this discrepancy is unclear.

Several double-blind, placebo-controlled studies have specifically tested kava for the treatment of menopause-related anxiety. ^{15,16, 38} In the most recent one, 40 women were given either kava plus standard hormone therapy or hormone therapy alone, for a period of six months. The results showed that women given kava experienced greater improvement in symptoms than those given hormone therapy alone.

Besides these placebo-controlled studies, one 6-month double-blind study compared kava against two standard anxiety drugs (oxazepam and bromazepam) in 174 people with anxiety symptoms.¹⁸ Improvement in HAM-A scores was about the same in all groups.

A 5-week, double-blind, placebo-controlled trial studied 40 people who had been taking standard antianxiety drugs (benzodiazepines) for an average duration of 20 months.¹⁷ Participants were gradually tapered off their medications and switched to kava or placebo. Individuals taking kava showed some improvement in anxiety symptoms. This would appear to indicate that kava can successfully substitute for benzodiazepine drugs. However, participants who were switched from benzodiazepines to placebo showed little to no increase in anxiety, suggesting perhaps that they didn't really need medication after all! Thus, the results of this study are hard to interpret. Note: This trial involved close medical supervision and very gradual tapering of benzodiazepine dosages. Do not discontinue antianxiety medications without such supervision, as withdrawal symptoms can be life-threatening!

One study purported to find evidence that kava helps reduce reactions to stressful situations, but because it lacked a placebo group, the results mean little.¹⁹

Dosage

Kava is usually sold in a standardized form where the total amount of kavalactones per pill is listed. For use as an antianxiety agent, the dose of kava should supply about 40 to 70 mg of kavalactones 3 times daily. The total daily dosage should not exceed 300 mg.

The proper dosage for insomnia is 210 mg of kavalactones 1 hour before bedtime.

Safety Issues

Up until recently, kava has been considered a safe herb. Animal studies have shown that kava dosages of up to 4 times normal cause no health problems, and 13 times the normal dosage causes only mild problems in rats.²⁰A study of 4,049 people who took a rather low dose of kava (70 mg of kavalactones daily) for 7 weeks found side effects in 1.5% of cases. These were mostly mild gastrointestinal complaints and allergic rashes.²¹ A 4-week study of 3,029 individuals given 240 mg of kavalactones daily showed a 2.3% incidence of basically the same side effects.²²

However, a growing number of case reports have raised alarm regarding kava. These cases indicate that occasionally, even normal doses of kava can cause severe liver injury.^25,26,36,37 Based on these reports, use of kava has been banned in Australia, Germany, and Canada. TNP recommends that anyone using kava should seek physician supervision to monitor for liver injury; anyone at special risk of liver damage (such as those who have existing liver disease, drink alcohol or take medications that can harm the liver) should avoid kava altogether. 

There are other safety concerns as well.  For example, kava should not be used by individuals who have had "acute dystonic reactions." These consist of spasms in the muscles of the neck and movements of the eyes, and are believed related to effects on dopamine. They are typically caused by antipsychotic drugs, which affect dopamine. Kava might trigger such reactions too.²⁴

At ordinary doses, kava does not appear to produce mental cloudiness.^27,28 However, high doses cause inebriation, and can lead to charges of driving under the influence of drugs.  

One study suggests that kava does not amplify the effects of alcohol.³² However, there is a case report indicating that kava can increase the effects of certain sedative drugs.³³ For this reason, kava probably should not be combined with any drugs that depress mental function. Kava should also not be combined with antipsychotic drugs or drugs used for Parkinson's disease, due to the potential for increased problems with movement.³⁴

The German Commission E monograph warns against the use of kava during pregnancy and nursing. Safety in young children and individuals with kidney disease has not been established.

Transitioning from Medications

If you're regularly taking Xanax or other drugs in the benzodiazepine family, switching to kava will be very difficult. You must seek a doctor's supervision, because withdrawal symptoms can be severe and even life-threatening. Additionally, if you are taking Xanax on an "as needed" basis to stop acute panic attacks, kava cannot be expected to have the same rapidity of action.

It may be easier to make the switch from milder antianxiety drugs, such as BuSpar, and antidepressants. Nonetheless, a doctor's supervision is still strongly advised.

Interactions You Should Know About

If you are taking

• Medications for insomnia or anxiety such as benzodiazepines: Do not take kava in addition to them.
• Antipsychotic drugs: Kava might increase the risk of a particular side effect consisting of sudden abnormal movements, called a dystonic reaction.
• Levodopa for Parkinson's disease: Kava might reduce its effectiveness.
• Alcohol, or medications that can irritate the liver, avoid kava. (Numerous medications have this potential.  Ask your physician to see if this concern applies to you.)

Last reviewed August 2002 by Medical Review Board

Back to Top