CRD Summary: The authors stated that short-term treatment with levodopa is effective and safe for restless legs syndrome, but evidence on long-term treatment is lacking. Given the wide variation in the primary studies, the poor reporting of methods and findings in the review, the use of unsuitable statistical methods and the questionable interpretation of safety data, these conclusions do not appear reliable.

CRD Commentary: The review question was clear and the search was adequate. The inclusion criteria were wide, particularly with respect to the outcomes, and no details were provided about the outcome measures reported (e.g. whether a high score was desirable). This makes it difficult to interpret the results, or even to determine whether any studies reported the primary outcome. The authors did not report whether measures were taken to reduce the risk of reviewer error and bias in the study selection, validity assessment and data extraction processes, such as decisions being made independently by more than one reviewer. The narrative review was not always consistent with the tables. The statistical methods used to pool the studies were designed for parallel-group data and are unsuitable for crossover studies. Subgroups were pooled inappropriately and significant statistical heterogeneity, which was evident in the forest plot for PLMS, was not discussed. The authors' conclusions about the safety of short-term levodopa are questionable in view of the increased risk of augmentation noted in the levodopa arms of 3 studies with durations of 3 days to 3 weeks. Given the wide variation in the primary studies, the poor reporting of methods and findings in the review, the use of unsuitable statistical methods and the questionable interpretation of the safety data, the authors' conclusions do not appear reliable.