Editing Suprachiasmatic nucleus (section)

== Clinical significance ==

=== Irregular sleep-wake rhythm disorder ===
[[Irregular sleep–wake rhythm|Irregular sleep-wake rhythm (ISWR) disorder]] is thought to be caused by structural damage to the SCN, decreased responsiveness of the circadian clock to light and other stimuli, and decreased exposure to light.<ref name=":3" /><ref>{{Cite journal |last1=Zee |first1=Phyllis C. |last2=Vitiello |first2=Michael V. |date=2009-06-01 |title=Circadian Rhythm Sleep Disorder: Irregular Sleep Wake Rhythm |journal=Sleep Medicine Clinics |series=Basics of Circadian Biology and Circadian Rhythm Sleep Disorders |language=en |volume=4 |issue=2 |pages=213–218 |doi=10.1016/j.jsmc.2009.01.009 |pmid=20160950 |pmc=2768129 |issn=1556-407X}}</ref> People who tend to stay indoors and limit their exposure to light experience decreased nocturnal melatonin production. The decrease in melatonin production at night corresponds with greater expression of SCN-generated wakefulness during night, causing irregular sleep patterns.<ref name=":3" />

=== Major depressive disorder ===
[[Major depressive disorder|Major depressive disorder (MDD)]] has been associated with altered circadian rhythms.<ref name=":13">{{Cite journal |last1=Landgraf |first1=Dominic |last2=Long |first2=Jaimie E. |last3=Proulx |first3=Christophe D. |last4=Barandas |first4=Rita |last5=Malinow |first5=Roberto |last6=Welsh |first6=David K. |date=2016-12-01 |title=Genetic Disruption of Circadian Rhythms in the Suprachiasmatic Nucleus Causes Helplessness, Behavioral Despair, and Anxiety-like Behavior in Mice |journal=Biological Psychiatry |series=Novel Signaling Mechanisms in Depression |language=en |volume=80 |issue=11 |pages=827–835 |doi=10.1016/j.biopsych.2016.03.1050 |pmid=27113500 |pmc=5102810 |issn=0006-3223}}</ref> Patients with MDD have weaker rhythms that express clock genes in the brain. When SCN rhythms were disturbed, anxiety-like behavior, weight gain, helplessness, and despair were reported in a study conducted with mice. Abnormal [[glucocorticoid]] levels occurred in mice with no ''[[BMAL1|Bmal1]]'' expression in the SCN.<ref name=":13" />

=== Alzheimer's disease ===
The functional disruption of the SCN can be observed in early stages of [[Alzheimer's disease|Alzheimer's disease (AD)]].<ref name=":22">{{Cite journal |last1=Weldemichael |first1=Dawit A. |last2=Grossberg |first2=George T. |date=2010-09-02 |title=Circadian Rhythm Disturbances in Patients with Alzheimer's Disease: A Review |journal=International Journal of Alzheimer's Disease |language=en |volume=2010 |pages=e716453 |doi=10.4061/2010/716453 |pmid=20862344 |pmc=2939436 |issn=2090-8024 |doi-access=free }}</ref> Changes in the SCN and melatonin secretion are major factors that cause circadian rhythm disturbances. These disturbances cause the normal physiology of sleep to change, such as the [[Circadian rhythm|biological clock]] and body temperature during rest.<ref name=":22" /> Patients with AD experience [[insomnia]], [[hypersomnia]], and other sleep disorders as a result of the degeneration of the SCN and changes in critical neurotransmitter concentrations.<ref name=":22" />