Valerian root is an herbal supplement that is often taken to improve sleep. Some people also take it to relieve anxiety or stress. Valerian root contains valerenic acid, which has dual effects. It works as a sedative in the body and also seems to influence the brain. It has been used for centuries to help with anxiety, but there is some evidence that it can also be effective for sleep problems. Valerian root is available in a few different forms, including capsules, tinctures and extracts.