Editing Developmental disorder (section)

=== Causes ===
The scientific study of the causes of developmental disorders involves many theories. Some of the major differences between these theories involves whether environment disrupts normal development, if abnormalities are pre-determined, or if they are products of human evolutionary history which become disorders in modern environments (''see [[evolutionary psychiatry]]'').<ref name="Karmiloff Annette">{{cite journal | author = Karmiloff Annette | title = Development itself is key to understanding developmental disorders | journal = Trends in Cognitive Sciences| volume =  2| issue = 10| pages =  389–398| doi=10.1016/S1364-6613(98)01230-3 | pmid=21227254 | date=October 1998| s2cid = 38117177 }}</ref>
Normal development occurs with a combination of contributions from both the environment and [[genetics]]. The theories vary in the part each factor has to play in normal development, thus affecting how the abnormalities are caused.<ref name="Karmiloff Annette"/>

One theory that supports environmental causes of developmental disorders involves stress in early childhood. Researcher and child psychiatrist [[Bruce D. Perry|Bruce D. Perry, M.D., Ph.D]], theorizes that developmental disorders can be caused by early childhood [[Traumatic memories|traumatization]].<ref name="Perry, Bruce D 2006, p.2">Perry, Bruce D. and Szalavitz, Maia. "The Boy Who Was Raised As A Dog", Basic Books, 2006, p.2. {{ISBN|978-0-465-05653-8}}</ref> In his works, he compares developmental disorders in traumatized children to adults with post-traumatic stress disorder, linking extreme environmental stress to the cause of developmental difficulties.<ref name="Perry, Bruce D 2006, p.2"/> Other stress theories suggest that even small stresses can accumulate to result in [[Emotional and behavioral disorders|emotional]], behavioral, or [[Rebellion|social disorders]] in children.<ref>Payne, Kim John. “Simplicity Parenting: Using the Extraordinary Power of Less to Raise Calmer, Happier, and More Secure Kids”, Ballantine Books, 2010, p. 9. {{ISBN|9780345507983}}</ref>

A 2017 study<ref>{{Cite web|url=https://www.ddduk.org/|title=Deciphering Developmental Disorders (DDD) project|website=www.ddduk.org|publisher=Wellcome Trust Sanger Institute|access-date=2017-01-27|archive-date=2019-10-19|archive-url=https://web.archive.org/web/20191019161535/https://www.ddduk.org/|url-status=live}}</ref><ref>{{Cite journal|last1=McRae|first1=Jeremy F.|last2=Clayton|first2=Stephen|last3=Fitzgerald|first3=Tomas W.|last4=Kaplanis|first4=Joanna|last5=Prigmore|first5=Elena|last6=Rajan|first6=Diana|last7=Sifrim|first7=Alejandro|last8=Aitken|first8=Stuart|last9=Akawi|first9=Nadia|year=2017|title=Prevalence and architecture of de novo mutations in developmental disorders|journal=Nature|volume=542|issue=7642|pages=433–438|doi=10.1038/nature21062|pmid=28135719|pmc=6016744|url=http://eprints.whiterose.ac.uk/114459/3/emss-78087.pdf|bibcode=2017Natur.542..433M|access-date=2019-07-05|archive-date=2019-04-27|archive-url=https://web.archive.org/web/20190427153310/http://eprints.whiterose.ac.uk/114459/3/emss-78087.pdf|url-status=live}}</ref> tested all 20,000 genes in about 4,300 families with children with rare developmental difficulties in the [[United Kingdom|UK]] and Ireland in order to identify if these difficulties had a genetic cause. They found 14 new developmental disorders caused by spontaneous genetic mutations not found in either parent (such as a fault in the [[CDK13 (gene)|CDK13 gene]]). They estimated that about one in 300 children are born with spontaneous genetic mutations associated with rare developmental disorders.<ref>{{Cite news|url=https://www.bbc.co.uk/news/health-38691622|title=Child gene study identifies new developmental disorders|last=Walsh|first=Fergus|date=2017-01-25|newspaper=BBC News|access-date=2017-01-27|archive-date=2019-04-17|archive-url=https://web.archive.org/web/20190417072259/https://www.bbc.co.uk/news/health-38691622|url-status=live}}</ref>