(HealthDay News) — Valerian, an herb native to Europe and Asia and introduced in the United States, is often marketed as a natural sleep aid.

But clinical research has yet to prove that the herb actually works in inducing sleep, the U.S. National Institutes of Health’s Office of Dietary Supplements says.

“Although the results of some studies suggest that valerian may be useful for insomnia and other sleep disorders, results of other studies do not,” the agency says. “Overall, the evidence from these trials for the sleep-promoting effects of valerian is inconclusive.”

Women who are pregnant and children under age 3 should not take supplements containing the herb, since its side effects have not completely been evaluated on these groups, the agency says.