Walters said the sleep disruption may cause the children to be inattentive and hyperactive due to sleep deprivation. The children also may have leg discomfort when sitting at their school desks that is relieved only by moving around, he said. An alternative possibility is that these disorders simply appear together frequently. Children with ADHD have a higher incidence of periodic limb movements of sleep than children who don't have ADHD, Walters said. Also, the parents of children with ADHD and periodic limb movements of sleep have a higher incidence of restless legs syndrome than other parents do.
Researchers also have another theory why levodopa improves the children's ADHD symptoms.
This could be why. Walters said the benefits of the levodopa appear to last long term. The next step to confirm these results is a double blind, placebo-control trial, he said. The drug should also be tested with children with ADHD who do not have these sleep disturbances, he said.