Editing Handedness (section)

===Health===
Studies have found a positive correlation between left-handedness and several specific physical and mental disorders and health problems, including:

*[[Low birth weight|Lower birth weight]] and complications at birth are positively correlated with left-handedness.<ref>{{cite journal |last1=Goodman |first1=Joshua |title=The Wages of Sinistrality: Handedness, Brain Structure, and Human Capital Accumulation |journal=Journal of Economic Perspectives |date=November 2014 |volume=28 |issue=4 |pages=193–212 |doi=10.1257/jep.28.4.193 }}</ref><ref>{{cite journal |last1=Kauko Heikkilä,a,1 Catharina E. M. Van Beijsterveldt,b Jari Haukka,c Matti Iivanainen,d,2 Aulikki Saari-Kemppainen,e |title=Triplets, birthweight, and handedness |journal=Proc Natl Acad Sci U S A |date=Jun 5, 2018 |volume=115 |issue=23 |pages=6076–6081 |doi=10.1073/pnas.1719567115 |doi-access=free |pmid=29760105 |pmc=6003315 |bibcode=2018PNAS..115.6076H }}</ref>
*A variety of neuropsychiatric and developmental disorders such as [[autism spectrum]],<ref>{{cite journal |title=Handedness in autism spectrum disorders and intellectually disabled children and adolescents - Contrasting caregivers' reports with assessments of hand preference |journal=Heliyon |date=2024 |doi=10.1016/j.heliyon.2024.e25935 |doi-access=free |pmid=38380041 |last1=Samadi |first1=S. A. |volume=10 |issue=4 |pages=e25935 |pmc=10877286 |bibcode=2024Heliy..1025935S }}</ref> [[bipolar disorder]], [[anxiety disorders]], [[schizophrenia]], and [[alcoholism]] have been associated with left- and mixed-handedness.<ref name="Ocklenburg"/><ref>{{cite journal | vauthors = Hirnstein M, Hugdahl K | title = Excess of non-right-handedness in schizophrenia: meta-analysis of gender effects and potential biases in handedness assessment | journal = The British Journal of Psychiatry | volume = 205 | issue = 4 | pages = 260–7 | date = October 2014 | pmid = 25274314 | doi = 10.1192/bjp.bp.113.137349 | doi-access = free | author-link2 = Kenneth Hugdahl }}</ref>
*A 2012 study showed that nearly 40% of children with [[cerebral palsy]] were left-handed,<ref>{{cite journal | vauthors = Lin KR, Prabhu V, Shah H, Kamath A, Joseph B | s2cid = 6972136 | title = Handedness in diplegic cerebral palsy | journal = Developmental Neurorehabilitation | volume = 15 | issue = 5 | pages = 386–9 | date = 2015 | pmid = 22758776 | doi = 10.3109/17518423.2012.696736 }}</ref> while another study demonstrated that left-handedness was associated with a 62% increased risk of [[Parkinson's disease]] in women, but not in men.<ref>{{cite journal | vauthors = Gardener H, Gao X, Chen H, Schwarzschild MA, Spiegelman D, Ascherio A | title = Prenatal and early life factors and risk of Parkinson's disease | journal = Movement Disorders | volume = 25 | issue = 11 | pages = 1560–7 | date = August 2010 | pmid = 20740569 | pmc = 3132935 | doi = 10.1002/mds.23339 }}</ref> Another study suggests that the risk of developing [[multiple sclerosis]] increases for left-handed women, but the effect is unknown for men at this point.<ref>{{cite journal | vauthors = Gardener H, Munger K, Chitnis T, Spiegelman D, Ascherio A | title = The relationship between handedness and risk of multiple sclerosis | journal = Multiple Sclerosis | volume = 15 | issue = 5 | pages = 587–92 | date = May 2009 | pmid = 19389750 | pmc = 2771381 | doi = 10.1177/1352458509102622 }}</ref> 
*Left-handed women may have a higher risk of [[breast cancer]] than right-handed women and the effect is greater in post-menopausal women.<ref>{{cite journal | vauthors = Fritschi L, Divitini M, Talbot-Smith A, Knuiman M | title = Left-handedness and risk of breast cancer | journal = British Journal of Cancer | volume = 97 | issue = 5 | pages = 686–7 | date = September 2007 | pmid = 17687338 | pmc = 2360366 | doi = 10.1038/sj.bjc.6603920 }}</ref>
*At least one study maintains that left-handers are more likely to suffer from [[heart disease]], and are more likely to have reduced longevity from [[cardiovascular]] causes.<ref>{{cite journal | vauthors = Hughes JR, Dorner E, Wind M | s2cid = 21369165 | title = Is the decreased longevity among left-handers related to an increase in heart disease? | journal = Clinical EEG and Neuroscience | volume = 39 | issue = 4 | pages = 182–4 | date = October 2008 | pmid = 19044215 | doi = 10.1177/155005940803900406 }}</ref>
*Left-handers may be more likely to suffer bone fractures.<ref>{{cite journal | vauthors = Luetters CM, Kelsey JL, Keegan TH, Quesenberry CP, Sidney S | s2cid = 32654176 | title = Left-handedness as a risk factor for fractures | journal = Osteoporosis International | volume = 14 | issue = 11 | pages = 918–22 | date = November 2003 | pmid = 14530828 | doi = 10.1007/s00198-003-1450-z }}</ref>
*Left-handers have a lower prevalence of [[arthritis]] and [[Ulcerative colitis|ulcer]].<ref>{{cite journal |last1=Wysocki |first1=C. J. |last2=McManus |first2=I. C. |title=Left-handers have a lower prevalence of arthritis and ulcer |journal=Laterality |date=March 2005 |volume=10 |issue=2 |pages=97–102 |doi=10.1080/13576500442000256 |pmid=15849026 |s2cid=34998957 }}</ref>
*One [[systematic review]] concluded, "Left-handers showed no systematic tendency to suffer from disorders of the immune system."<ref>{{cite web|url=https://www.psychologytoday.com/blog/brain-myths/201303/three-myths-and-three-facts-about-left-handers|title=Three Myths and Three Facts About Left-Handers|work=Psychology Today}}</ref>

As handedness is a highly heritable trait associated with various medical conditions, and because many of these conditions could have presented a Darwinian fitness challenge in ancestral populations, this indicates left-handedness may have previously been rarer than it currently is, due to natural selection. However, on average, left-handers have been found to have an advantage in fighting and competitive, interactive sports, which could have increased their reproductive success in ancestral populations.<ref>{{cite news|last1=Knight|first1=Will | name-list-style = vanc |title=Left-handers win in hand-to-hand combat|url=https://www.newscientist.com/article/dn6773-left-handers-win-in-hand-to-hand-combat/|access-date=27 October 2016|work=[[New Scientist]]|date=8 December 2004|archive-url=https://web.archive.org/web/20161027125658/https://www.newscientist.com/article/dn6773-left-handers-win-in-hand-to-hand-combat/|archive-date=27 October 2016|url-status=live}}</ref>