Causes of Restless Legs Syndrome, From Genetics to Pregnancy

For years, doctors have actually known more about how to treat restless legs syndrome (RLS) than about what causes it. They've discovered that symptoms sometimes improve with medications that trigger the production of dopamine, a chemical in the brain that regulates movement and feelings of pleasure. But there is some evidence that dopamine is only one of many factors in causing RLS.

It's suspected that RLS acts up especially at night because dopamine levels follow the body's circadian rhythm, and decrease as the body winds down for sleep, says Charlene Gamaldo, MD, assistant professor of neurology at Johns Hopkins University in Baltimore.

Scientists also suspect that the abnormal levels of dopamine that can trigger RLS in some people may be caused by low iron in the blood. But even then, there's often not a good explanation as to why one person experiences symptoms and another doesn't. Whether or not there's an underlying condition that contributes to RLS divides it into two types: primary and secondary.

Primary RLS
When all outside factors and other conditions have been ruled out as a cause for RLS symptoms, the condition can be classified as primary RLS. It is usually found in early onset cases, before the ages of 35 to 45, when there are no other identifiable causes. It has long been suspected that primary RLS can be hereditary, and in 2007, scientists at Emory University discovered a gene variant that more than doubles a person's risk of developing RLS.

Mimi Gauthier, a movie set decorator in New Orleans, recalls her father's battle with RLS: He always had to shake out his legs repeatedly before he could sit in his lounge chair and snooze, and he napped frequently during the day. Gauthier's own legs started bothering her at age 6, and today at 47 she suffers from severe RLS that leaves her constantly exhausted and sleep deprived.