From the Journals: Herbs and ... Health Article

From the Journals

Anxiety disorders are among the most commonly diagnosed psychiatric illnesses, affecting some 40 million adults each year in the United States, women more often than men. They encompass a wide variety of diagnoses, including generalized anxiety disorder, panic disorder, post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), and phobias. Anxiety disorders can be treated effectively with psychotherapy and drugs such as benzodiazepine tranquilizers, antidepressants, and beta blockers. But major surveys suggest that many people seek complementary and alternative medicine to relieve their symptoms.

Various studies have found some herbs and dietary supplements helpful for mild to moderate anxiety. But a review of the evidence published in the August 15, 2007, issue of American Family Physician found little or no scientific support for the use of most such treatments. One notable exception was the herbal supplement kava. Here's a rundown on the evidence for and against the top contenders:

Kava (Piper methysticum). Usually prepared as a tea, kava is made from the dried rhizome (root) of a shrub found throughout the South Pacific, where it is used for social, ceremonial, and medicinal purposes. Kava is reported to have a relaxing effect without impairing mental and physical function. Several randomized controlled trials have shown that kava is slightly superior to a placebo in relieving anxiety. One trial indicated that it was as effective as the anti-anxiety drug buspirone (Buspar).

Kava inhibits an enzyme used by the liver to metabolize several medications, so it's important to consider possible drug interactions before using this herb. Do not take alcohol, barbiturates, benzodiazepine drugs, or alprazolam (Xanax) while taking kava. You should not take kava if you have liver problems. Kava should not be used for longer than four months because its health effects beyond that haven't been established. With long-term use, a rash or skin yellowing may develop, but these symptoms usually go away when you stop taking the herb. Rare cases of serious liver disease have led several countries to ban kava, but it remains available in the United States. (The FDA has issued warnings but questions the accuracy of the liver toxicity reports.) As with many herbs, different plant parts can have different types of activity; it may be that some preparations are potentially more harmful to the liver than others. Look for supplements made from the root (rhizome) rather than the leaves or stems.

Inositol. This supplement, a member of the B-vitamin complex, has been found somewhat helpful for the treatment of panic disorder in two controlled trials. One study showed that inositol was superior to a placebo in reducing symptoms. The other found it to be as effective in treating panic disorder as the selective serotonin reuptake inhibitor (SSRI) fluvoxamine. The side effects are mild and similar to those of SSRIs. Results of studies for OCD have been mixed.

St. John's wort (Hypericum perforatum). No controlled trials have found that St. John's wort has any beneficial effects on generalized anxiety disorder, PTSD, OCD, or any other anxiety disorder. (The evidence favoring its use in mild-to-moderate depression is better.) In one controlled trial, it was effective in treating somatoform disorder — persistent physical symptoms with no apparent physical cause. Somatoform disorder is not an anxiety disorder but is often accompanied by anxiety. Drug interactions can be a problem with St. John's wort. It interferes with the activity of many drugs, including carbamazepine (an anti-epileptic drug), cyclosporine (an anti-rejection medication), the anticancer drug irinotecan, birth control pills, simvastatin (a statin), antidepressants, the blood-thinner warfarin, and digoxin (a heart drug).

Valerian (Valeriana officinalis) and passion flower (Passiflora incarnata L.). Valerian and passion flower are considered sedatives and are sometimes combined in the same supplement. Although valerian has long been used to treat anxiety, most studies are small and poorly designed. One small controlled trial found valerian to be no more effective than a placebo in the treatment of generalized anxiety disorder. In a study comparing passion flower with a tranquilizer, both drugs appeared to reduce patients' anxiety, but there was no placebo group for comparison. The Cochrane Collaboration, an international not-for-profit organization, has concluded that there is insufficient evidence to support the use of either valerian or passion flower in the treatment of anxiety.

5-HTP (5-hydroxytryptophan). This substance is a serotonin precursor — a naturally occurring amino acid from which the body makes the neurotransmitter serotonin. The supplement 5-HTP is made from the seeds of an African plant and used to treat depression, anxiety, and insomnia. A small randomized controlled trial found 5-HTP to be more effective than a placebo in preventing an experimentally induced panic attack. In another trial, it was slightly better than a placebo for the relief of mixed anxiety disorders, but not nearly as effective as the antidepressant and antianxiety drug clomipramine (Anafranil). Serotonin precursors were temporarily removed from the market several years ago after users of a related substance, L-tryptophan, developed a potentially fatal neurologic condition called eosinophilia-myalgia syndrome. Although the problem may have resulted from impurities traceable to one manufacturer, there's still uncertainly about the safety of these drugs, and clinicians are advised to warn patients against them.

Caution always warranted

To sum up, there is good evidence that kava can help in treating mild to moderate symptoms of anxiety disorders in people who are not using alcohol or taking medications metabolized by the liver. There is some evidence for inositol in treating panic disorder and possibly OCD. Some evidence favors 5-HTP for the treatment of anxiety, but safety is a concern. There's not enough evidence to recommend St. John's wort, valerian, and passion flower for anxiety disorders.

Herbal medicines and dietary supplements are not regulated as drugs, so their safety and effectiveness are not established. And there's no guarantee that you're getting exactly what appears on a supplement's label. Herbal supplements in particular can have many active constituents, not all of which have been tested or even identified. If you're considering an herbal or dietary supplement to treat symptoms of anxiety (or any other condition, for that matter) discuss it with your clinician first. If you decide to go ahead, check for reliable brands through independent sources such as ConsumerLab.com, LLC (www.consumerlab.com). For more information about herbal supplements, visit the Web sites of the National Center for Complementary and Alternative Medicine (nccam.nih.gov/health), the Alternative Medicine Foundation (www.amfoundation.org), and MedlinePlus (www.nlm.nih.gov/medlineplus/druginformation.html).