Alterations of microRNAs (miRNAs) may be involved in the pathophysiology of central hypersomnias, suggests a study in the September issue of SLEEP. Results show that the levels of four miRNAs differed in plasma from patients with type 1 narcolepsy, type 2 narcolepsy and idiopathic hypersomnia. According to the authors, looking at the targets of these miRNAs will promote understanding of the pathogenesis of central hypersomnias.