Kicking Up a Storm? It Could Be ADHD
Because children with ADHD often have RLS and a related problem called periodic limb movements of sleep, the researchers questioned whether adults with RLS might also have ADHD that had gone unrecognized.
"The leg discomfort from RLS could cause people to be more hyperactive and distractible, and being tired could cause people to be more inattentive," Wagner says.
"We often miss the diagnosis in children since the symptoms are so benign, or parents think they are related to growing pains, or the children don't know what it means," says Wagner.
Wagner and colleagues speculate that RLS and ADHD could be genetically linked, which might explain why they appear together frequently, or that the leg discomfort from RLS and associated sleep disruption could cause ADHD-like symptoms.
Another theory holds that both ADHD and RLS may be caused by a shortage in the brain of dopamine, a chemical messenger that is partly responsible for the control of movement; lack of dopamine-producing nerve cells in the brain is a major hallmark of Parkinson's disease.
In studies of children with ADHD who do not respond well to the standard therapy with Ritalin and are treated instead with drugs that enhance dopamine production and transport in the brain, Walker and colleagues found that the therapy also appeared to improve symptoms of RLS.
The researchers say that adults with ADHD and RLS may have improvement of symptoms with drugs that enhance dopamine use in the brain. Although in patients with Parkinson's disease such drugs can cause jerky or uncontrolled movements, their primary side effect in people with ADHD tend to be nausea, vomiting, lightheadedness, or fainting.
"People from the Massachusetts General Hospital at Harvard University have estimated that only about 30% of the people have ADHD by itself," says Michael E. Finkel, MD, a neurologist at the Cleveland Clinic in Naples, Fla., who commented on the RLS/ADHD study for WebMD.
"Those who have the ADHD 'complex' have other disorders which can be recognized and treated," he says, so the more a doctor knows about a patient's medical history, the better positioned he is to treat that patient.