Decision making in restless legs syndrome.

The dopamine system is implicated in reward-based decision making with explicit information (decision making under risk) and implicit probabilities (decision making under ambiguity). Although the pathophysiology of restless legs syndrome (RLS) is not yet fully understood, the genetic factors, iron status, and dopaminergic system are thought to play a role. RLS provides an opportunity to test the dopaminergic hypothesis in a drug-free population and to characterize reward processing using decision-making paradigms. We investigated impulsivity, impulse control disorders, and decision making in 50 untreated patients with primary RLS compared with 60 sex- and age-matched normal controls using one night of polysomnography recording, a structured psychiatric interview, and questionnaires (RLS Severity Scale, Beck Depression Inventory, and Urgency Premeditation Perseverance Impulsive Behavior Scale). Subjects performed the Iowa Gambling Task to assess decision making under ambiguity and the Game of Dice Task to assess decision making under risk. Patients with RLS showed selective changes in decision making on the Iowa Gambling Task and normal decision making on the Game of Dice Task compared with controls. Patients with RLS had greater depressive symptoms than controls, but no difference was found in impulsivity, impulse control disorders, or addictive behaviors. Clinical and polysomnographic variables were unrelated to decision-making performance. Results indicate reduced decision-making performance under ambiguity in drug-free patients with RLS. From a clinical perspective, when using dopaminergic medication to treat RLS, patients with abnormal baseline behaviors should be closely monitored.