PHILADELPHIA, PA (American Academy of Neurology) — Adults who have restless legs syndrome are more likely to also have attention deficit hyperactivity disorder (ADHD) than adults who don't have the sleep disorder, according to research presented during the American Academy of Neurology's 53rd Annual Meeting in Philadelphia, PA, May 5-11, 2001.

In restless legs syndrome (RLS), patients feel sensations of discomfort in their legs when they are sleeping or not active. The discomfort is relieved by moving or stimulating the legs. RLS can cause interrupted sleep and fatigue or sleepiness during the day.

ADHD is a genetic, biochemical disorder characterized by inattention, restlessness, distractability and impulsivity.

For the study, researchers at the New Jersey Neuroscience Institute at JFK Medical Center in Edison tested 56 adults with restless legs syndrome for ADHD symptoms and compared them to 77 people who did not have RLS. Thirty-nine percent of the patients met the criteria for "possible" ADHD, compared to 14 percent of controls. Of those, 21 percent of the patients met the criteria for "highly probable" ADHD, compared to four percent of controls.

Twenty-one of the 33 patients and controls with possible ADHD underwent additional, objective psychological testing. Of those, 100 percent of the patients had a profile consistent with that of ADHD, as did 86 percent of the controls. RLS patients with ADHD also had greater anxiety symptoms than controls with ADHD.

Those patients who had both restless legs and ADHD also had more severe RLS symptoms than the RLS patients without ADHD.

Researchers have a few theories why the disorders appear to be linked.

"The leg discomfort from RLS could cause people to be more hyperactive and distractable," said study author Mary L. Wagner, Pharm.D., of Rutgers University in Piscataway, NJ . "And being tired from having your sleep disrupted could cause people to be more inattentive. But it's not proven that having RLS leads to having ADHD. It could be that these disorders simply appear together frequently -- they may be genetically linked."

Another theory is that both disorders may be caused by a lack of dopamine in the brain. Dopamine is responsible for transmitting signals within the brain. A lack of dopamine can leave patients unable to control their movements normally. Evidence for this theory is that both disorders respond well to drugs that promote dopamine action in the brain.

"People with RLS should also be tested for ADHD, and vice versa," Wagner said. "That way these disorders can be diagnosed and treated more effectively."

The risk of ADHD or RLS is greater in people with a family history of the disorder. "A patient with ADHD or his or her family may be more likely to also have RLS, but more study is needed on this," Wagner said.