Editing Sleep disorder (section)

=== Major depressive disorder (MDD) ===
Sleep disturbances (insomnia or hypersomnia) - though not a necessary diagnostic criterion - are one of the most frequent symptoms of individuals with major depressive disorder (MDD).<ref>{{cite journal | vauthors = Liu X, Buysse DJ, Gentzler AL, Kiss E, Mayer L, Kapornai K, Vetró A, Kovacs M | display-authors = 6 | title = Insomnia and hypersomnia associated with depressive phenomenology and comorbidity in childhood depression | journal = Sleep | volume = 30 | issue = 1 | pages = 83–90 | date = January 2007 | pmid = 17310868 | doi = 10.1093/sleep/30.1.83 | doi-access = free }}</ref> Among individuals with MDD, insomnia and hypersomnia have prevalence estimates of 88% and 27%, respectively, whereas individuals with insomnia have a threefold increased risk of developing MDD.<ref name=":21">{{cite journal | vauthors = Murphy MJ, Peterson MJ | title = Sleep Disturbances in Depression | journal = Sleep Medicine Clinics | volume = 10 | issue = 1 | pages = 17–23 | date = March 2015 | pmid = 26055669 | pmc = 5678925 | doi = 10.1016/j.jsmc.2014.11.009 }}</ref> Depressed mood and sleep efficiency strongly co-vary, and while sleep regulation problems may precede depressive episodes, such depressive episodes may also precipitate sleep deprivation.<ref name=":21" /> Fatigue, as well as sleep disturbances such as irregular and excessive sleepiness, are linked to symptoms of depression.<ref name=":21" /> Recent research has even pointed to sleep problems and fatigues as potential driving forces bridging MDD symptoms to those of co-occurring generalized anxiety disorder.<ref name="Coussement & Heeren-2022">{{cite journal | vauthors = Coussement C, Heeren A | title = Sleep problems as a transdiagnostic hub bridging impaired attention control, generalized anxiety, and depression | journal = Journal of Affective Disorders | volume = 296 | pages = 305–308 | date = January 2022 | pmid = 34606807 | doi = 10.1016/j.jad.2021.09.092 | s2cid = 238357084 }}</ref>