Kava Overview

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. Typically, each participant would drink two or three bowls of chewed 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 Other named kavalactones include kavain, methysticin, and dihydromethysticin.

High doses of kava extracts are thought to cause muscle relaxation and even paralysis (without loss of consciousness) at very high doses. ^{2 3 4} Kava also has local anesthetic properties, 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. ⁵ However, more recent studies have found an interaction. ⁶ The early researchers may have missed the connection because kava appears to affect somewhat unusual parts of the brain.

Note: An accumulation of case reports suggests that kava products may rarely cause severe liver injury, and this has led to a banning of kava by many countries. See Safety Issues for more information.

Anxiety

There have been at least 11 placebo-controlled studies of kava, involving a total of more than 700 people. ⁷ Most found kava helpful for anxiety symptoms.

One of the best of these was a 6-month, double-blind study that tested kava's effectiveness in 100 people with various forms of anxiety. ⁸ 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 one week. ⁹ The reason for this discrepancy is unclear.

Several double-blind, placebo-controlled studies have specifically tested kava for the treatment of the anxiety that often occurs during menopause . ¹⁰ In one study, 40 women were given either kava plus standard hormone therapy or hormone therapy alone for a period of 6 months. The results showed that women given kava experienced greater improvement in symptoms than those given hormone therapy alone.

However, not all studies have been positive. One double-blind, placebo-controlled study failed to find kava effective for people with generalized anxiety disorder (GAD). ¹¹ Another study failed to find kava more effective than placebo for people with both anxiety and insomnia. ¹² 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. ¹³ Improvement in HAM-A scores was about the same in all groups. Another study found kava equally effective as the drugs buspirone and opipramol. ¹⁴ A 5-week, double-blind, placebo-controlled trial studied 40 people who had been taking standard anti-anxiety drugs ( benzodiazepines ) for an average duration of 20 months. ¹⁵ 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 be substituted 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 anti-anxiety medications without supervision. Withdrawal symptoms can be life-threatening.

One study purported to find evidence that kava helps reduce reactions to stressful situations . ¹⁶ Although, the results mean little because the study lacked a placebo group.

A typical dosage of kava when used for treatment of anxiety is 300 mg daily of a product standardized to contain 70% kavalactones. A lower dose of 150 mg daily has also been tested, but may be less effective. ¹⁷ The typical dosage for insomnia is 210 mg of kavalactones 1 hour before bedtime.

1. Meyer HJ, Kretzschmar R. Kawa pyrone—a new kind of substance group of central muscle relaxants of the mephenesin type [translated from German]. Klin Wochenschr. 1966;44:902-903.
2. Meyer HJ. Pharmacology of the active compounds of the kava rhizome ( Piper methysticum Forst) [translated from German]. Arch Int Pharmacodyn Ther. 1962;138:505-536.
3. Meyer HJ, May HU. Local anaesthetic properties of natural Kava pyrones [translated from German]. Klin Wochenschr. 1964;42:407.
4. Meyer HJ, Kretzschmar R. Kawa pyrone—a new kind of substance group of central muscle relaxants of the mephenesin type [translated from German]. Klin Wochenschr. 1966;44:902-903.
5. Davies LP, Drew CA, Duffield P, Johnston GA, Jamieson DD. Kava pyrones and resin: studies on GABAA, GABAB and benzodiazepine binding sites in rodent brain. Pharmacol Toxicol. 71(2):120-6.
6. Jussofie A, Schmiz A, Hiemke C. Kavapyrone enriched extract from Piper methysticum as modulator of the GABA binding site in different regions of rat brain. Psychopharmacology (Berl). 1994;116:469-474.
7. Volz HP, Kieser M. Kava-kava extract WS 1490 versus placebo in anxiety disorders--a randomized placebo-controlled 25-week outpatient trial. Pharmacopsychiatry. 30(1):1-5.
8. Volz HP, Kieser M. Kava-kava extract WS 1490 versus placebo in anxiety disorders--a randomized placebo-controlled 25-week outpatient trial. Pharmacopsychiatry. 30(1):1-5.
9. Kinzler E, Kromer J, Lehmann E. Effect of a special kava extract in patients with anxiety-, tension-, and excitation states of non-psychotic genesis. Double blind study with placebos over 4 weeks [translated from German]. Arzneimittelforschung. 1991;41:584-588.
10. Warnecke G, Pfaender H, Gerster G, et al. Efficacy of an extract of kava root in patients with climacteric syndrome. A double blind study with a new mono-preparation [translated from German]. Z Phytother. 1990;11:81-86.
11. Connor KM, Davidson JR. A placebo-controlled study of Kava kava in generalized anxiety disorder. Int Clin Psychopharmacol. 2002;17:185-188.
12. Jacobs BP, Bent S, Tice JA, Blackwell T, Cummings SR. An internet-based randomized, placebo-controlled trial of kava and valerian for anxiety and insomnia. Medicine (Baltimore). 84(4):197-207.
13. Woelk H, Kapoula O, Lehrl S, et al. The treatment of patients with anxiety. A double blind study: kava extract WS 1490 versus benzodiazepine [translated from German]. Z Allg Med. 1993;69:271-277.
14. Boerner RJ, Sommer H, Berger W, Kuhn U, Schmidt U, Mannel M. 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. 10 Suppl 4():38-49.
15. Malsch U, Klement S. Randomized placebo-controlled double-blind clinical trial of a special extract of kava roots (WS 1490) in patients with anxiety disorders of non-psychotic origin [abstract]. Eur Phytojournal [serial online]. 2000(1). ESCOP website. Available at: http://www.escop.com/issue_1. Accessed May 10, 2001.
16. Cropley M, Cave Z. Effect of kava and valerian on physiological responses to psychological stress assessed under laboratory conditions [abstract]. FACT. 2001;6:76.
17. Gastpar M, Klimm HD. Treatment of anxiety, tension and restlessness states with Kava special extract WS 1490 in general practice: a randomized placebo-controlled double-blind multicenter trial. Phytomedicine. 10(8):631-9.