The specific causes of restless legs syndrome (RLS) are not known. It was once thought to be due to disease in the blood vessels of the legs or in the nerves in the legs that control leg movement and sensation, but both of these suggestions have been rejected.
RLS may be related to abnormalities in brain chemicals (neurotransmitters) that help regulate muscle movements, or to abnormalities in the part of the central nervous system that controls automatic movements. Research is still being done in these areas.
RLS can sometimes be caused by an underlying medical condition (secondary RLS); however, most of the time the cause is not clear.