non-24-hour sleep-wake syndrome non-24 SCTID:230496009 ICD10:G47.24 hypernychthemeral syndrome GARD:0010949 ICD10:G47.2 http://www.case.edu/EpSO.owl#NonTwentyFourHourSleepWakeSyndrome circadian rhythm sleep disorder, free running type circadian rhythm sleep disorder, free-running type Non-24-hour sleep-wake disorder (non-24 disorder), also known as hypernychthemeral syndrome, is a circadian rhythm sleep disorder characterized by non-synchronization to a 24-hour day leading to insomnia and daytime sleepiness with sometimes severe associated manifestations. Orphanet:73267 non 24 hour sleep wake disorder MONDO:0019137 circadian rhythm sleep disorder