Is restless legs syndrome in the genes, not in the head?

ATLANTA — Scientists have linked certain genes to restless legs syndrome, demonstrating that the condition — which is sometimes greeted with skepticism — is biologically based.

New studies published this week in two medical journals are being called the first to identify specific genes responsible for the disorder.

For decades, people who have complained of the condition have had to contend with critics who said their problems were mostly in their heads. Symptoms, which often are worse at night, include twitching or jerking movements, and tingling or crawling sensations.

Research published in the New England Journal of Medicine linked a common gene variation to nighttime leg-twitching. It involved people in Iceland and the United States.

A second study in Nature Genetics identified the same gene variation and two others in Germans and Canadians with restless legs syndrome.

"This discovery demonstrates the power of genetics not only for uncovering the biological causes of disease, but also for defining diseases such as RLS and establishing them as medical conditions," said Dr. Kari Stefansson, a prominent Icelandic scientist who co-authored the New England Journal study.

"It feels like something crawling inside your legs, biting on you," said Betty Shaw, a 68-year-old florist in Covington, Ga., who was diagnosed with the condition. So was her 43-year-old daughter.

The first study looked at blood samples from more than 1,000 Icelanders and Americans, comparing the DNA of leg twitchers to the DNA of people without the symptom. Scientists found a certain variation in the genome that, they say, probably accounts for 50 percent of restless legs cases.

The second study compared the DNA of 400 people who had a family history of the syndrome with the DNA of 1,600 who did not. It found variations in three areas of the genome that each were responsible for a 50 percent increase in the risk for the syndrome.

More research is needed to develop a full explanation of the causes of restless legs syndrome. The New England Journal study indicates as many as 65 percent of adults carry the gene variation that can lead to symptoms, said Dr. David Rye, an Emory University neurologist who was another co-author.