Editing Circadian rhythm (section)

=== Causes of disruption to circadian rhythms ===

==== Indoor lighting ====
Lighting requirements for circadian regulation are not simply the same as those for vision; planning of indoor lighting in offices and institutions is beginning to take this into account.<ref>{{cite journal | vauthors = Rea MS, Figueiro M, Bullough J |date=May 2002 |title=Circadian photobiology: an emerging framework for lighting practice and research |journal=Lighting Research & Technology |volume=34 |issue=3 |pages=177–187 |doi=10.1191/1365782802lt057oa |s2cid=109776194}}</ref> Animal studies on the effects of light in laboratory conditions have until recently considered light intensity ([[irradiance]]) but not color, which can be shown to "act as an essential regulator of biological timing in more natural settings".<ref>{{cite journal | vauthors = Walmsley L, Hanna L, Mouland J, Martial F, West A, Smedley AR, Bechtold DA, Webb AR, Lucas RJ, Brown TM | title = Colour as a signal for entraining the mammalian circadian clock | journal = PLOS Biology | volume = 13 | issue = 4 | pages = e1002127 | date = April 2015 | pmid = 25884537 | pmc = 4401556 | doi = 10.1371/journal.pbio.1002127 | doi-access = free }}</ref>

Blue LED lighting suppresses [[melatonin]] production five times more than the orange-yellow [[Sodium-vapor lamp|high-pressure sodium (HPS) light]]; a [[metal halide lamp]], which is white light, suppresses melatonin at a rate more than three times greater than HPS.<ref>{{Cite journal | vauthors = Hardt R |date=1970-01-01 |title=The Dangers of LED-Blue light-The Suppression of Melatonin-Resulting in-Insomnia-And Cancers {{pipe}} Robert Hardt |url=https://www.academia.edu/5960717 |access-date=2016-12-24 |website=Academia.edu}}{{Dead link|date=December 2021|bot=InternetArchiveBot|fix-attempted=yes}}</ref> [[Biology of depression#Circadian rhythm|Depression symptoms]] from long term nighttime light exposure can be undone by returning to a normal cycle.<ref>{{cite journal | vauthors = Bedrosian TA, Nelson RJ | title = Timing of light exposure affects mood and brain circuits | journal = Translational Psychiatry | volume = 7 | issue = 1 | pages = e1017 | date = January 2017 | pmid = 28140399 | pmc = 5299389 | doi = 10.1038/tp.2016.262 }}</ref>

==== Airline pilots and cabin crew ====
Due to the nature of work of airline pilots, who often cross several time zones and regions of sunlight and darkness in one day, and spend many hours awake both day and night, they are often unable to maintain sleep patterns that correspond to the natural human circadian rhythm; this situation can easily lead to [[fatigue (physical)|fatigue]]. The [[NTSB]] cites this as contributing to many accidents,<ref>[http://www.aviationweek.com/aw/jsp_includes/articlePrint.jsp?storyID=news/FATIGex.xml&headLine=null]{{dead link|date=December 2016}}</ref> and has conducted several research studies in order to find methods of combating fatigue in pilots.<ref>Circadian Rhythm Disruption and Flying. FAA at https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/Circadian_Rhythm.pdf {{Webarchive|url=https://web.archive.org/web/20170501112906/https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/Circadian_Rhythm.pdf|date=2017-05-01}}</ref>

==== Effect of drugs ====
Studies conducted on both animals and humans show major bidirectional relationships between the circadian system and abusive drugs. It is indicated that these abusive drugs affect the central circadian pacemaker. Individuals with substance use disorder display disrupted rhythms. These disrupted rhythms can increase the risk for substance abuse and relapse. It is possible that genetic and/or environmental disturbances to the normal sleep and wake cycle can increase the susceptibility to addiction.<ref name="Logan">{{cite journal |vauthors=Logan RW, Williams WP, McClung CA |date=June 2014 |title=Circadian rhythms and addiction: mechanistic insights and future directions |journal=Behavioral Neuroscience |volume=128 |issue=3 |pages=387–412 |doi=10.1037/a0036268 |pmc=4041815 |pmid=24731209}}</ref>

It is difficult to determine if a disturbance in the circadian rhythm is at fault for an increase in prevalence for substance abuse—or if other environmental factors such as stress are to blame.
Changes to the circadian rhythm and sleep occur once an individual begins abusing drugs and alcohol. Once an individual stops using drugs and alcohol, the circadian rhythm continues to be disrupted.<ref name="Logan" />

[[Alcohol (drug)|Alcohol]] consumption disrupts circadian rhythms, with acute intake causing dose-dependent alterations in melatonin and cortisol levels, as well as core body temperature, which normalize the following morning, while chronic alcohol use leads to more severe and persistent disruptions that are associated with alcohol use disorders (AUD) and withdrawal symptoms.<ref>{{cite journal |last1=Meyrel |first1=M |last2=Rolland |first2=B |last3=Geoffroy |first3=PA |title=Alterations in circadian rhythms following alcohol use: A systematic review. |journal=Progress in Neuro-psychopharmacology & Biological Psychiatry |date=20 April 2020 |volume=99 |pages=109831 |doi=10.1016/j.pnpbp.2019.109831 |pmid=31809833}}</ref>

The stabilization of sleep and the circadian rhythm might possibly help to reduce the vulnerability to addiction and reduce the chances of relapse.<ref name="Logan" />

Circadian rhythms and [[CLOCK|clock]] genes expressed in brain regions outside the [[suprachiasmatic nucleus]] may significantly influence the effects produced by drugs such as [[cocaine]].<ref>{{Cite journal |last1=Falcón |first1=Edgardo |last2=McClung |first2=Colleen A. |date=2009-01-01 |title=A role for the circadian genes in drug addiction |journal=Neuropharmacology |series=Frontiers in Addiction Research: Celebrating the 35th Anniversary of the National Institute on Drug Abuse |volume=56 |issue=Suppl 1 |pages=91–96 |doi=10.1016/j.neuropharm.2008.06.054 |pmid=18644396 |issn=0028-3908|pmc=2635341 }}</ref> Moreover, genetic manipulations of clock genes profoundly affect cocaine's actions.<ref>{{cite journal |vauthors=Prosser RA, Glass JD |date=June 2015 |title=Assessing ethanol's actions in the suprachiasmatic circadian clock using in vivo and in vitro approaches |journal=Alcohol |volume=49 |issue=4 |pages=321–339 |doi=10.1016/j.alcohol.2014.07.016 |pmc=4402095 |pmid=25457753}}</ref>