Modern science, though, is split on whether the herb works. Some studies have indicated that it can ease insomnia, but few rigorous clinical trials have put valerian to the test.
For the most recent study, reported in the journal Menopause, researchers in Iran randomly assigned 100 postmenopausal women with insomnia to take either two valerian capsules or inactive placebo capsules every day for a month.
"Valerian improves the quality of sleep in women with menopause who are experiencing insomnia," wrote Simin Taavoni and colleagues at Tehran University.
"Findings from this study add support to the reported effectiveness of valerian in the clinical management of insomnia."
Overall, their study found, 30 percent of the women assigned to valerian reported an improvement in their sleep quality, which includes factors such as how long it takes to fall asleep at night and how often a person wakes up overnight.
In contrast, only four percent of women taking the placebo reported better sleep.
Sleep problems tend to become more common as people age, with studies suggesting that about half of older adults have insomnia symptoms, such as trouble falling asleep or staying asleep. For women, menopausal hot flashes and night sweats can add to their sleep problems.
Women in the study reported no side effects, Taavoni`s team said. General studies suggest that any side effects from the herb are mild, such as a headache or upset stomach.
The current findings are "encouraging" said Jerome Sarris of the University of Melbourne in Australia, who was not involved in the study but has researched herbal approaches to treating insomnia, anxiety and depression.
"There is no harm in trying it," he added.
But there is currently no research on the safety of long-term use of valerian, according to the U.S. National Center for Complementary and Alternative Medicine.
Despite the positive findings in the current study, there are still questions about valerian`s effectiveness. In a recent review of clinical trials on alternative remedies for insomnia, Sarris and his colleagues found only weak evidence that valerian -- or other herbs -- work.
There was better evidence in support of yoga, tai chi and acupressure.
Sarris said that future studies should look at valerian`s effects on other measures of sleep, such as the total amount of time that people taking the herb are able to stay asleep, and their daytime functioning.