Editing Schizophrenia (section)

===Environmental===
{{Further|Prenatal nutrition|Prenatal stress|Neuroplastic effects of pollution}}

Environmental factors, each associated with a slight risk of developing schizophrenia in later life include [[intrauterine hypoxia|oxygen deprivation]], infection, [[prenatal maternal stress]], and malnutrition in the mother during prenatal development.<ref name=Stilo2019>{{cite journal |vauthors=Stilo SA, Murray RM |title=Non-Genetic Factors in Schizophrenia |journal=Current Psychiatry Reports |volume=21 |issue=10 |page=100 |date=14 September 2019 |pmid=31522306 |doi=10.1007/s11920-019-1091-3 |pmc=6745031 }}</ref> A risk is associated with maternal obesity, in increasing [[oxidative stress]], and dysregulating the dopamine and serotonin pathways.<ref>{{cite journal |vauthors=Cirulli F, Musillo C, Berry A |s2cid=211029692 |title=Maternal Obesity as a Risk Factor for Brain Development and Mental Health in the Offspring |journal=Neuroscience|date= 5 February 2020 |volume=447 |pages=122–135 |pmid=32032668|doi= 10.1016/j.neuroscience.2020.01.023|hdl=11573/1387747 |hdl-access=free }}</ref> Both maternal stress and infection have been demonstrated to alter fetal [[neurodevelopment]] through an increase of pro-inflammatory [[cytokine]]s.<ref name=Upthegrove2020>{{cite book |vauthors=Upthegrove R, Khandaker GM |title=Neuroinflammation and Schizophrenia |chapter=Cytokines, Oxidative Stress and Cellular Markers of Inflammation in Schizophrenia | series = Current Topics in Behavioral Neurosciences|volume=44 |pages=49–66 |date=2020 |pmid=31115797 |doi= 10.1007/7854_2018_88|isbn=978-3-030-39140-9 |s2cid=162169817 |chapter-url= http://pure-oai.bham.ac.uk/ws/files/74984176/Upthegrove_Khandaker_Cytokines_oxidative_stress_and_cellular_markers_of_inflammation_in_schizophrenia_Current_Topics_in_Behavioral_Neurosciences_2019.pdf }}</ref> There is a slighter risk associated with being born in the winter or spring possibly due to [[vitamin D deficiency]]<ref name=Chiang2016>{{cite journal |vauthors=Chiang M, Natarajan R, Fan X |s2cid= 206926835 |title=Vitamin D in schizophrenia: a clinical review |journal= Evidence-Based Mental Health |volume=19 |issue=1 |pages=6–9 |date= February 2016 |pmid=26767392 |doi=10.1136/eb-2015-102117 |pmc=10699337 }}</ref> or a prenatal [[viral infection]].<ref name=BMJ07/> Other infections during pregnancy or around the time of birth that have been linked to an increased risk include infections by ''[[Toxoplasma gondii]]'' and ''[[Chlamydia infection|Chlamydia]]''.<ref>{{cite journal | vauthors = Arias I, Sorlozano A, Villegas E, de Dios Luna J, McKenney K, Cervilla J, Gutierrez B, Gutierrez J | title = Infectious agents associated with schizophrenia: a meta-analysis | journal = Schizophrenia Research | volume = 136 | issue = 1–3 | pages = 128–136 | date = April 2012 | pmid = 22104141 | doi = 10.1016/j.schres.2011.10.026 | hdl-access = free | s2cid = 2687441 | hdl = 10481/90076 }}</ref> The increased risk is about five to eight percent.<ref name=yolken>{{cite journal | vauthors = Yolken R | title = Viruses and schizophrenia: a focus on herpes simplex virus | journal = Herpes | volume = 11 | issue = Suppl 2 | pages = 83A–88A | date = June 2004 | pmid = 15319094 }}</ref> Viral infections of the brain during childhood are also linked to a risk of schizophrenia during adulthood.<ref>{{cite journal | vauthors = Khandaker GM | title = Childhood infection and adult schizophrenia: a meta-analysis of population-based studies. | journal = Schizophr. Res. | volume = 139 | issue = 1–3 | pages = 161–168 |date = August 2012 | pmid = 22704639 | pmc = 3485564 | doi = 10.1016/j.schres.2012.05.023}}</ref> [[Human interaction with cats|Cat exposure]] is also associated with an increased risk of broadly defined schizophrenia-related disorders, with an [[odds ratio]] of 2.4.<ref>{{cite journal | title = Cat Ownership and Schizophrenia-Related Disorders and Psychotic-Like Experiences: A Systematic Review and Meta-Analysis | journal = Schizophrenia Bulletin | volume = 50 | issue = 3 | pages = 489–495 | date = May 2024 | pmid = 38491934 | pmc = 11059805 | doi = 10.1093/schbul/sbad168 | vauthors = McGrath JJ, Lim CC, Saha S }}</ref>

[[Adverse childhood experiences]] (ACEs), severe forms of which are classed as [[childhood trauma]], range from being bullied or abused, to the death of a parent.<ref name=Pearce2019>{{cite journal |vauthors=Pearce J, Murray C, Larkin W |title=Childhood adversity and trauma:experiences of professionals trained to routinely enquire about childhood adversity |journal=Heliyon |volume=5 |issue=7 |page=e01900 |date=July 2019 |pmid=31372522 |doi=10.1016/j.heliyon.2019.e01900|doi-access=free |pmc=6658729 |bibcode=2019Heliy...501900P }}</ref> Many adverse childhood experiences can cause [[toxic stress]] and increase the risk of psychosis.<ref name=Pearce2019/><ref>{{cite journal | vauthors = Dvir Y, Denietolis B, Frazier JA | title = Childhood trauma and psychosis | journal = Child and Adolescent Psychiatric Clinics of North America | volume = 22 | issue = 4 | pages = 629–641 | date = October 2013 | pmid = 24012077 | doi = 10.1016/j.chc.2013.04.006 | s2cid = 40053289 }}</ref><ref>{{cite journal | vauthors = Misiak B, Krefft M, Bielawski T, Moustafa AA, Sąsiadek MM, Frydecka D | s2cid = 21614845 | title = Toward a unified theory of childhood trauma and psychosis: A comprehensive review of epidemiological, clinical, neuropsychological and biological findings | journal = Neuroscience and Biobehavioral Reviews | volume = 75 | pages = 393–406 | date = April 2017 | pmid = 28216171 | doi = 10.1016/j.neubiorev.2017.02.015 }}</ref> Chronic trauma, including ACEs, can promote lasting inflammatory dysregulation throughout the nervous system.<ref name=Nettis2020>{{cite book | vauthors = Nettis MA, Pariante CM, Mondelli V | title = Neuroinflammation and Schizophrenia | chapter = Early-Life Adversity, Systemic Inflammation and Comorbid Physical and Psychiatric Illnesses of Adult Life | series = Current Topics in Behavioral Neurosciences| volume = 44 | pages = 207–225 | date = 2020 | pmid = 30895531 | doi = 10.1007/7854_2019_89 | isbn = 978-3-030-39140-9 | s2cid = 84842249 | chapter-url = https://kclpure.kcl.ac.uk/portal/en/publications/earlylife-adversity-systemic-inflammation-and-comorbid-physical-and-psychiatric-illnesses-of-adult-life(d2cdfc38-19e7-4918-80f1-5525e6ff45bf).html}}</ref> It is suggested that early stress may contribute to the development of schizophrenia through these alterations in the immune system.<ref name= Nettis2020/> Schizophrenia was the last diagnosis to benefit from the link made between ACEs and adult mental health outcomes.<ref>{{cite journal |vauthors=Guloksuz S, van Os J |title=The slow death of the concept of schizophrenia and the painful birth of the psychosis spectrum |journal=Psychological Medicine |volume=48 |issue=2 |pages=229–244 |date=January 2018 |pmid=28689498 |doi=10.1017/S0033291717001775|doi-access=free }}</ref>

Living in an [[Risk factors of schizophrenia#Urbanicity|urban environment]] during childhood or as an adult has consistently been found to increase the risk of schizophrenia by a factor of two,<ref name= Lancet2009/><ref>{{cite journal |vauthors= Costa E, Silva JA, Steffen RE |title=Urban environment and psychiatric disorders: a review of the neuroscience and biology |journal=Metabolism: Clinical and Experimental |volume=100S |page=153940 |date=November 2019 |pmid=31610855|doi=10.1016/j.metabol.2019.07.004|s2cid=204704312 }}</ref> even after taking into account [[Recreational drug use|drug use]], [[ethnic group]], and size of [[social group]].<ref>{{cite journal | vauthors = van Os J | title = Does the urban environment cause psychosis? | journal = The British Journal of Psychiatry | volume = 184 | issue = 4 | pages = 287–8 | date = April 2004 | pmid = 15056569 | doi = 10.1192/bjp.184.4.287 | doi-access = free }}</ref> A possible link between the [[Neuroplastic effects of pollution|urban environment and pollution]] has been suggested to be the cause of the elevated risk of schizophrenia.<ref>{{cite journal |vauthors=Attademo L, Bernardini F, Garinella R, Compton MT |s2cid=25505446 |title= Environmental pollution and risk of psychotic disorders: A review of the science to date |journal=Schizophrenia Research |volume=181 |pages=55–59 |date=March 2017 |pmid=27720315 |doi=10.1016/j.schres.2016.10.003}}</ref> Other risk factors include [[social isolation]], immigration related to social adversity and racial discrimination, family dysfunction, unemployment, and poor housing conditions.<ref name=BMJ07/><ref>{{cite journal | vauthors = Selten JP, Cantor-Graae E, Kahn RS | s2cid = 21391349 | title = Migration and schizophrenia | journal = Current Opinion in Psychiatry | volume = 20 | issue = 2 | pages = 111–115 | date = March 2007 | pmid = 17278906 | doi = 10.1097/YCO.0b013e328017f68e }}</ref> Having a [[paternal age effect|father older than 40 years]], or parents younger than 20 years are also associated with schizophrenia.<ref name= Lancet2016 /><ref>{{cite journal | vauthors = Sharma R, Agarwal A, Rohra VK, Assidi M, Abu-Elmagd M, Turki RF | title = Effects of increased paternal age on sperm quality, reproductive outcome and associated epigenetic risks to offspring | journal = Reproductive Biology and Endocrinology | volume = 13 | pages = 35 | date = April 2015 | pmid = 25928123 | pmc = 4455614 | doi = 10.1186/s12958-015-0028-x | doi-access = free }}</ref>

====Substance use====
{{Further|Risk factors of schizophrenia#Substance use|Substance-induced psychosis}}

About half of those with schizophrenia use [[recreational drugs]] including [[alcohol (drug)|alcohol]], tobacco, and [[cannabis (drug)|cannabis]] excessively.<ref name=Gregg2007/><ref>{{cite journal | vauthors = Sagud M, Mihaljević-Peles A, Mück-Seler D, Pivac N, Vuksan-Cusa B, Brataljenović T, Jakovljević M | title = Smoking and schizophrenia | journal = Psychiatria Danubina | volume = 21 | issue = 3 | pages = 371–375 | date = September 2009 | pmid = 19794359 }}</ref> Use of [[stimulant]]s such as [[amphetamine]] and [[cocaine]] can lead to a temporary [[stimulant psychosis]], which presents very similarly to schizophrenia. Rarely, alcohol use can also result in a similar [[Alcoholic hallucinosis|alcohol-related psychosis]].<ref name= BMJ07/><ref name=alcohol>{{Cite journal |url= http://www.emedicine.com/med/topic3113.htm |title=Alcohol-Related Psychosis |access-date=27 September 2006 | vauthors = Larson M |date=30 March 2006 |journal=EMedicine |url-status=live |archive-url= https://web.archive.org/web/20081109011819/http://www.emedicine.com/MED/topic3113.htm |archive-date=9 November 2008}}</ref> Drugs may also be used as coping mechanisms by people who have schizophrenia, to deal with depression, [[anxiety]], boredom, and [[loneliness]].<ref name=Gregg2007>{{cite journal | vauthors = Gregg L, Barrowclough C, Haddock G | title = Reasons for increased substance use in psychosis | journal = Clinical Psychology Review | volume = 27 | issue = 4 | pages = 494–510 | date = May 2007 | pmid = 17240501 | doi = 10.1016/j.cpr.2006.09.004 }}</ref><ref name=Leweke08>{{cite journal | vauthors = Leweke FM, Koethe D | title = Cannabis and psychiatric disorders: it is not only addiction | journal = Addiction Biology | volume = 13 | issue = 2 | pages = 264–75 | date = June 2008 | pmid = 18482435 | doi = 10.1111/j.1369-1600.2008.00106.x | s2cid = 205400285 }}</ref> The use of cannabis and tobacco are not associated with the development of cognitive deficits, and sometimes a reverse relationship is found where their use improves these symptoms.<ref name=Vidailhet2013>{{cite journal | vauthors = Vidailhet P | title = [First-episode psychosis, cognitive difficulties and remediation]. | journal = L'Encéphale | date = September 2013 | volume = 39 | issue = Suppl 2 | language= fr| pages = S83-92 | doi = 10.1016/S0013-7006(13)70101-5 | pmid=24084427}}</ref> However, [[substance use disorder]]s are associated with an increased risk of suicide, and a poor response to treatment.<ref name= Khokhar2018>{{cite book |vauthors=Khokhar JY, Henricks AM, Sullivan ED, Green AI |title=Apprentices to Genius: A tribute to Solomon H. Snyder |chapter=Unique Effects of Clozapine: A Pharmacological Perspective |series=Advances in Pharmacology |volume=82 |pages=137–162 |date=2018 |pmid=29413518|doi=10.1016/bs.apha.2017.09.009|pmc=7197512 |isbn=978-0128140871 }}</ref><ref>{{cite journal |vauthors=Bighelli I, Rodolico A, García-Mieres H, et al |title=Psychosocial and psychological interventions for relapse prevention in schizophrenia: a systematic review and network meta-analysis |journal=Lancet Psychiatry |volume=8 |issue=11 |pages=969–980 |date=November 2021 |pmid=34653393 |doi=10.1016/S2215-0366(21)00243-1 |s2cid=239003358 |doi-access=free |url=https://boris.unibe.ch/160225/8/Bighelli_LancetPsychiatry_2021.pdf }}</ref>

[[Long-term effects of cannabis#Chronic psychosis and schizophrenia spectrum disorders|Cannabis use]] may be a contributory factor in the development of schizophrenia, potentially increasing the risk of the disease in those who are already at risk.<ref name= Patel2020>{{cite journal |vauthors=Patel S, Khan S, M S, Hamid P |title=The Association Between Cannabis Use and Schizophrenia: Causative or Curative? A Systematic Review |journal= [[Cureus]] |volume=12 |issue=7 |pages=e9309 |date=July 2020 |pmid=32839678 |pmc=7442038 |doi=10.7759/cureus.9309 |doi-access=free |url=}}</ref><ref name= Hasan2020>{{cite journal |vauthors=Hasan A, von Keller R, Friemel CM, Hall W, Schneider M, Koethe D, Leweke FM, Strube W, Hoch E |title=Cannabis use and psychosis: a review of reviews |journal=Eur Arch Psychiatry Clin Neurosci |volume=270 |issue=4 |pages= 403–412 |date=June 2020 |pmid=31563981 |doi=10.1007/s00406-019-01068-z |s2cid=203567900 |url=}}</ref><ref>{{cite web |title=Causes — Schizophrenia | url= https://www.nhs.uk/mental-health/conditions/schizophrenia/causes/ |publisher= UK [[National Health Service]] |date=11 November 2019 |access-date= 8 December 2021}}</ref> The increased risk may require the presence of certain genes within an individual.<ref name= Parakh2013>{{cite journal | vauthors = Parakh P, Basu D | title = Cannabis and psychosis: have we found the missing links? | journal = [[Asian Journal of Psychiatry]] | volume = 6 | issue = 4 | pages = 281–287 | date = August 2013 | pmid = 23810133 | doi = 10.1016/j.ajp.2013.03.012 | type = Review | quote = Cannabis acts as a component cause of psychosis, that is, it increases the risk of psychosis in people with certain genetic or environmental vulnerabilities, though by itself, it is neither a sufficient nor a necessary cause of psychosis. }}</ref> Its use is associated with doubling the rate.<ref>{{cite journal | vauthors = Ortiz-Medina MB, Perea M, Torales J, Ventriglio A, Vitrani G, Aguilar L, Roncero C | title = Cannabis consumption and psychosis or schizophrenia development | journal = The International Journal of Social Psychiatry | volume = 64 | issue = 7 | pages = 690–704 | date = November 2018 | pmid = 30442059 | doi = 10.1177/0020764018801690 | s2cid = 53563635 }}</ref>