An investigation published in the current issue of Psychotherapy and Psychosomatics by a group of Danish investigators explores the characteristics of restorative sleep. One of the major changes introduced by the DSM-5 has been to consider non-restorative sleep (NRS) as a specific insomnia disorder. Since there is paucity of study on the co-morbidity of NRS and major depression, the Authors have analyzed the full data set from the Danish General Suburban Population Study (GESUS), a cross-sectional investigation of the adult Danish suburban population in the Næstved Municipality situated approximately 70 km south of Copenhagen.
The study took place between January 2010 and October 2013. In the medical health questionnaires to be completed were the WHO-5 that contain items on quality of sleep, and the Major Depression Inventory (MDI) as well as information about sleep length, lifetime depression, and prescribing of antidepressants.
Results showed that, in the general population, both short and long sleep lengths had a prevalence of NRS of approximately 50%, but in persons with adequate sleep length the prevalence was around 24%. However, in persons with a current major depression the prevalence of NRS was around 44% for adequate sleep length but significantly higher in short or long sleep lengths. Authors concluded that by using the specific NRS item within the WHO-5, it is possible to establish whether a person has an NRS-specific diagnosis which warrants independent clinical attention, no matter whether the diagnosis of major depression is present or not.