Can a Root Get to the Problem of Insomnia?

The Ache: Nearly half of Americans have at least occasional insomnia, according to the nonprofit National Sleep Foundation.

The Claim: A natural sedative called valerian root can help.

The Verdict: Some studies find valerian root helps combat insomnia, while others find it's no better than a placebo. Doctors say it's relatively safe so there's no harm in trying it.

Valerian is a flowering plant used for centuries as a remedy for insomnia and anxiety. The herbal remedies are made from its roots and can have an unpleasant, earthy smell.

Valerenic acid, an ingredient of the root, acts on chemical pathways in the brain that control a person's level of anxiety or relaxation, according to scientific literature. At least 68 companies sell products in the U.S. containing valerian, says Spins LLC, a Schaumburg, Ill., market-research firm. It is available in capsules and tablets, as well as bedtime teas and a tincture, a liquid you can put under your tongue or mix with water.

Valerian has been shown to reduce anxiety in rats. But the results of dozens of studies with humans remain unconvincing, scientists say. In a review updated earlier this month, Natural Standard Research Collaboration, a Cambridge, Mass., scientist group that evaluates natural therapies, gave valerian a "C" grade for insomnia and anxiety, which means it considers the evidence to be unclear.

Preparations of the herb, including the amount of valerenic acid, vary widely from study to study, making it hard to draw firm conclusions, says Catherine Ulbricht, co-founder of Natural Standard and a pharmacist at Massachusetts General Hospital in Boston. Some studies tested blends of valerian with other herbs, such as lemon balm, a minty plant purported to be calming, she adds.

"There really isn't any compelling scientific evidence to use valerian as a sleep aid," says Meir Kryger, a professor of medicine at Yale University School of Medicine in New Haven, Conn. Most of the studies measure patients' subjective assessment of their sleep improvement instead of objective evidence from a sleep lab, he adds.

Many of the studies on valerian are small or lack placebo controls. In recent years, two larger placebo-controlled studies have been published. A study of 100 menopausal women, published in 2011, found 30% of women taking valerian twice daily for a month had improved sleep as measured by a questionnaire, compared with 4% in a group getting a placebo.

Another study of 119 cancer patients with difficulty sleeping found valerian before bedtime for two months had no significant effect on sleep scores calculated from a questionnaire filled out before the study and after two months. But even though the overall scores showed no difference, the patients taking valerian did show improvement on several narrower measures. "When we dug a little deeper and looked at specific questions, valerian did help people sleep more hours at night and [go to] sleep a little faster," says study co-author Debra L. Barton, an associate professor of oncology at the Mayo Clinic in Rochester, Minn. Another questionnaire found valerian reduced fatigue, which is a common problem among cancer patients.

The herb can cause headaches or tiredness the morning after, according to the National Institutes of Health's National Center for Complementary and Alternative Medicine. Avoid taking valerian at the same time as medication that can cause drowsiness, as the effects could be additive, adds Massachusetts General's Dr. Ulbricht.