It is thought that RLS and Parkinson’s disease may be caused by a similar problem, namely disruptions in the neurotransmitter dopamine. This is not fully understood, however. Regardless, RLS may be present in individuals who have Parkinson’s disease, with a prevalence ranging from 0 to 20.8 percent, varying based on the study. Parkinson’s disease often involves a sense of restlessness (called akathisia) that overlap with RLS, which may make it difficult to differntiate between the disorders. When both conditions are present, RLS usually occurs after Parkinson’s disease has become apparent.