Study Selection: 173 publications were retrieved. Articles related to the association between idiopathic RLS and depression, anxiety, and mood disorders were reviewed. In total, 32 epidemiologic studies were identified. These studies were reviewed in detail and ranked according to quality.Data Extraction: Data were extracted on the basis of relevance to the topic. Epidemiologic studies were assessed using 3 parameters: methodology, data quality, and generalizability of the results. Each factor was scored from 1 (high quality) to 4 (low quality), giving a total score of between 3 and 12 for each study.Results and Conclusions: RLS and mood disorders are frequently comorbid. Recognition and appropriate treatment of comorbid RLS are particularly important in patients with psychiatric disorders, as RLS is a common medical reason for insomnia, and antidepressant use may exacerbate sensory symptoms.