Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
Q: Context: Restless legs syndrome (RLS), also known as Willis-Ekbom disease, is a sensorimotor disorder that can result in considerable sleep disruption. This narrative review provides an overview of RLS diagnosis and reports epidemiologic evidence for an association between RLS and mood disorders. Possible links between RLS, sleep disturbances, and mood disorders are considered, and theoretical pathophysiologic pathways are discussed. Finally, pharmacologic therapies for RLS are summarized. A PubMed search was performed using the search term restless legs syndrome in combination with affective/anxiety, antidepressants, anxiety/anxiety disorder, attention deficit hyperactivity disorder, depression/depressive disorder, mood/mood disorder, neuropsychiatric, panic/panic disorder, psychiatric disorder, and psychosis. English-language articles published between January 1993 and May 2013 were retrieved. Additional studies were identified from the reference lists of relevant publications. 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 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. 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. 
 Question: Willis-Ekbom disease is also known as?
A: 
restless legs syndrome