Period limb movement disorder (PLMD) is characterized by rhythmic limb movement that occurs while you are asleep. Movements vary in severity, and typically affect the legs but can affect the arms as well. They can last from a few minutes to several hours. Many people with PLMD experience no symptoms, but some experience restless leg syndrome, or an uncomfortable sensation in the limbs. This condition can also contribute to insomnia or fatigue. The cause of PLMD is unknown, but it may be caused by abnormalities in the nervous system, certain diseases including Parkinson’s disease or narcolepsy, or some medications including antidepressants. PLMD is most often diagnosed by friends or family as they usually notice the disorder before you do, but can also be diagnosed with a sleep test. The is no known cure for PLMD, but it can be treated with drugs including Parkinson’s disease drugs, anticonvulsants, narcotics, and benzodiazepines. Antidepressants, caffeine, and low iron levels can worsen PLMD.