The main cause of RLS is unknown. Researchers are investigating neurologic (nervous system) problems that may arise either in the spinal cord or the brain. One current theory suggests that a deficiency in a brain chemical called dopamine causes restless legs syndrome.
RLS may often have a genetic basis, particularly in those who develop it before age 40. When the condition occurs in older adults, it is most likely due to a neurological problem.
People with RLS often have a family history of the disorder. Researchers have detected at least six genetic locations or factors that might be responsible for this condition. Two of the genes are associated with spinal cord development. None of the genes have been associated with dopamine or iron-regulating systems, though these are considered likely causes of the condition.
Dopamine and Neurologic Abnormalities in the Brain. A variety of studies support the theory that an imbalance in neurotransmitters (chemical messengers in the brain), notably dopamine, may play a part in RLS. Dopamine triggers numerous nerve impulses that affect muscle movement. The effect is similar to what happens in Parkinson's disease. Moreover, drugs that increase dopamine levels treat both disorders. However, Parkinson's disease itself does not seem to increase the risk for RLS. Nor does RLS early in life predispose a person to Parkinson's later on.
Review Date: 10/15/2010
Reviewed By: Reviewed by: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.