ROCHESTER, Minn., Dec. 30 (UPI) -- Roughly six percent of children with insomnia may in fact have restless legs syndrome and possibly an iron deficiency report U.S. researchers.

Restless legs syndrome causes pain in the legs around bedtime and sometimes unpleasant skin sensations. Sufferers cannot resist moving about to relieve the discomfort and, as a result, seldom get enough sleep. A new study by the Mayo Clinic in Rochester, Minn., shows that 6 percent of the children at the organization's sleep clinic have restless legs syndrome.

"It's been known for decades that children have 'growing pains,'" said sleep specialist Dr. Suresh Kotagal. "Studies by other investigators have now shown that growing pains in some children may actually be restless leg syndrome."

The most common risk factors for the disease are family history of restless legs syndrome and iron deficiency. There may also be a connection between restless legs syndrome and attention deficit hyperactivity disorder. The treatments for both conditions address a similar chemical imbalance.