According to WebMD, valerian is likely safe for most people when used appropriately on a short-term basis. Some possible side effects from valerian include uneasiness, excitability, headache and insomnia. The safety of long-term valerian usage is unknown.
According to WebMD, women should avoid using valerian when pregnant or breastfeeding, as there is insufficient information on the safety of this medicinal herb during pregnancy and breastfeeding. Valerian acts as a sedative for the brain and nervous system. Most people use valerian to treat sleep disorders, but it is also used for epilepsy, mild tremors, depression and ADHD. Some women use valerian for menstrual cramps and symptoms related to menopause.