Editing Polar night (section)

== Effects on sleep and mental health ==
Numerous analyses have been conducted to examine the effects of polar night on humans. In [[Tromsø (city)|Tromsø, Norway]], a city located at 69 degrees north, there is a 2 month long polar night, lasting from mid-November to mid-January. An analysis was conducted based on 2015-16 data from a health survey that involved residents of the region over age 40, with the goal being to analyze the seasonal variation of sleeping patterns in Tromsø. The study found that there was a higher prevalence of [[insomnia]] among men in the fall and winter months, but not among women. However, overall, sleep duration varied little to none throughout the year despite the extreme changes in daylight; it is worthwhile to note that a factor in this result may be the significant amount of [[Lighting|artificial light]] in Tromsø.<ref name=":0">{{Cite journal |last1=Sivertsen |first1=Børge |last2=Friborg |first2=Oddgeir |last3=Pallesen |first3=Ståle |last4=Vedaa |first4=Øystein |last5=Hopstock |first5=Laila Arnesdatter |date=2021-03-04 |title=Sleep in the land of the midnight sun and polar night: The Tromsø study |url=https://www.tandfonline.com/doi/full/10.1080/07420528.2020.1845191 |journal=Chronobiology International |language=en |volume=38 |issue=3 |pages=334–342 |doi=10.1080/07420528.2020.1845191 |issn=0742-0528 |pmid=33249932 |s2cid=227237010 |hdl-access=free |hdl=11250/2755604}}</ref>

A similar study was conducted among men who overwintered at [[Belgrano II Base|Belgrano II]], an Argentine research station in [[Antarctica]]. The station is located at 77 degrees south, resulting in a polar night 4 months in length. The study was conducted across 5 different winter campaigns in the 2010s, bringing in a total of 82 participants. The study found that participants generally slept for longer periods of time in the summer months than the winter months. Additionally, greater amounts of [[social jetlag]] were observed in the winter months.<ref name=":1">{{Cite journal |last1=Tortello |first1=C. |last2=Folgueira |first2=A. |last3=Lopez |first3=J. M. |last4=Didier Garnham |first4=F. |last5=Sala Lozano |first5=E. |last6=Rivero |first6=M. S. |last7=Simonelli |first7=G. |last8=Vigo |first8=D. E. |last9=Plano |first9=S. A. |date=2023-09-24 |title=Chronotype delay and sleep disturbances shaped by the Antarctic polar night |journal=Scientific Reports |language=en |volume=13 |issue=1 |pages=15957 |bibcode=2023NatSR..1315957T |doi=10.1038/s41598-023-43102-0 |issn=2045-2322 |pmc=10518309 |pmid=37743400}}</ref>

A third study aimed to examine the mental health of 88 Korean crew members at two different research stations in Antarctica, [[King Sejong Station]] and [[Jang Bogo Station]]. No crew members had been diagnosed with a [[mental illness]] prior to the study. While in Antarctica, 7 of the 88 crew members were diagnosed with a mental illness during early winter. The mental illnesses included [[Insomnia|insomnia disorder]] (3 diagnosed), [[depressive disorder]] (1 diagnosed), [[adjustment disorder]] (2 diagnosed), and [[alcohol use disorder]] (1 diagnosed).<ref name=":2">{{Cite journal |last1=Kang |first1=Jae Myeong |last2=Cho |first2=Seong-Jin |last3=Cho |first3=Seo-Eun |last4=Bang |first4=Taemo |last5=Chae |first5=Byung Do |last6=Yi |first6=Eojin |last7=Bae |first7=Seung Min |last8=Na |first8=Kyoung-Sae |last9=Jung |first9=Jaehun |last10=Kang |first10=Seung-Gul |date=2022-08-10 |title=Mood and Sleep Status and Mental Disorders During Prolonged Winter-Over Residence in Two Korean Antarctic Stations |journal=Nature and Science of Sleep |language=English |volume=14 |pages=1387–1396 |doi=10.2147/NSS.S370659 |pmc=9379312 |pmid=35982827 |doi-access=free}}</ref>

Overall, both Antarctic studies showed a lower amount of sleep beginning at the start of winter, while the study from the Korean bases also showed an onset of mental health problems at that time.<ref name=":1" /><ref name=":2" /> While the study from Tromsø did not show a similar drop in sleep duration as the Antarctic studies (perhaps due to the high amounts of artificial light), it did show an increased amount of insomnia in men during winter;<ref name=":0" /> therefore, the polar night was shown to have sleep and/or mental health effects in all three studies.