FRIDAY, July 29 (HealthDay News) -- New research is casting doubt on the effectiveness of kava and valerian root, two popular herbal remedies, with investigators finding they provided users with no more symptom relief than a placebo.

Kava, commonly used for anxiety, and valerian, used for insomnia, both worked as well as an inactive placebo when administered to 391 participants recruited via the Internet from 45 states.

According to the University of California, San Francisco team, anxiety scores decreased by 25 percent for patients taking a placebo, versus 21 percent for people taking either kava or valerian.

Effects on insomnia were about the same, with both the placebo and the herbal remedies decreasing scores by about 50 percent.

Most side effects were comparable between groups, although patients taking valerian reported a higher rate of diarrhea.

Based on the findings, the UCSF group concludes that any symptom improvement "may not be attributed to the biological effects of kava or valerian, and if attributable are no greater than the effect of placebo." They point out that the two herbal remedies are among the most popular sold today, with estimated annual U.S. sales of over $28 million.

The study is published in the July issue of Medicine.

More information

The National Institutes of Health has more about anxiety.