Editing Dyslexia (section)

===Gene–environment interaction===
The contribution of gene–environment interaction to reading disability, which estimates the proportion of variance associated with a person's environment and the proportion associated with their genes, has been intensely studied using [[twin studies]]. Both environmental and genetic factors appear to contribute to reading development. Studies examining the influence of environmental factors such as parental education<ref>{{cite journal |title=Parental Education Moderates Genetic Influences on Reading Disability |journal=Psychol. Sci. |volume=19 |issue=11 |pages=1124–30 |date=November 2008 |pmid=19076484 |pmc=2605635 |doi=10.1111/j.1467-9280.2008.02213.x |last1=Friend |first1=A |last2=Defries |first2=J. C. |last3=Olson |first3=R. K.}}</ref> and teaching quality<ref>{{cite journal |bibcode=2010Sci...328..512T|title=Teacher Quality Moderates the Genetic Effects on Early Reading|journal=Science|volume=328|issue=5977|pages=512–4|last1=Taylor|first1=J.|last2=Roehrig|first2=A. D.|last3=Hensler|first3=B. Soden|last4=Connor|first4=C. M.|last5=Schatschneider|first5=C.|year=2010|doi=10.1126/science.1186149|pmid=20413504|pmc=2905841}}</ref> have determined that genetics have greater influence in supportive, rather than less optimal, environments.<ref name=pmid19209992>{{cite journal |last1=Pennington |first1=Bruce F. |last2=McGrath |first2=Lauren M. |last3=Rosenberg |first3=Jenni |last4=Barnard |first4=Holly |last5=Smith |first5=Shelley D. |last6=Willcutt |first6=Erik G. |last7=Friend |first7=Angela |last8=Defries |first8=John C. |last9=Olson |first9=Richard K.  |date=January 2009 |title=Gene × Environment Interactions in Reading Disability and Attention-Deficit/Hyperactivity Disorder |journal=Developmental Psychology |volume=45 |issue=1 |pages=77–89 |doi=10.1037/a0014549 |pmid=19209992 |pmc=2743891}}</ref> However, more optimal conditions may just allow those genetic risk factors to account for more of the variance in outcome because the environmental risk factors have been minimized.<ref name=pmid19209992/>

As environment plays a large role in learning and memory, it is likely that [[epigenetic]] modifications play an important role in reading ability. Measures of [[gene expression]], [[Histone#Histone modification|histone modifications]], and [[methylation]] in the human periphery are used to study epigenetic processes; however, all of these have limitations in the extrapolation of results for application to the human brain.<ref>{{cite journal |last1=Roth |first1=Tania L. |last2=Roth |first2=Eric D. |last3=Sweatt |first3=J. David |s2cid=23229766 |date=September 2010  |title=Epigenetic regulation of genes in learning and memory |journal=Essays in Biochemistry |volume=48 |issue=1 |pages=263–74 |pmid=20822498 |doi=10.1042/bse0480263}}</ref><ref>{{cite journal |last1=Smith |first1=Shelley D. |title=Approach to epigenetic analysis in language disorders |journal=Journal of Neurodevelopmental Disorders |date=December 2011 |volume=3 |issue=4 |pages=356–364 |doi=10.1007/s11689-011-9099-y |pmid=22113455 |pmc=3261263 |issn=1866-1947}}</ref>

====Language====
The [[orthographic depth|orthographic complexity]] of a language directly affects how difficult it is to learn to read it.<ref name="BrunswickMcDougall2010">
Paulesu, Eraldo; Brunswick, Nicola and Paganelli, Federica (2010).  "Cross-cultural differences in unimpaired and dyslexic reading: Behavioral and functional anatomical observations in readers of regular and irregular orthographies. Chapter 12 in [https://books.google.com/books?id=0vJ5AgAAQBAJ&pg=PA266 Reading and Dyslexia in Different Orthographies] {{webarchive|url=https://web.archive.org/web/20170109135414/https://books.google.com/books?id=0vJ5AgAAQBAJ&pg=PA266 |date=9 January 2017 }}.  Eds. Nicola Brunswick, Siné McDougall, and Paul de Mornay Davies. Psychology Press. {{ISBN|9781135167813}}</ref>{{rp|266}} English and French have comparatively "deep" [[phonemic orthographies]] within the [[Latin alphabet]] [[writing system]], with complex structures employing spelling patterns on several levels: letter-sound correspondence, syllables, and [[morpheme]]s.<ref name="DickinsonNeuman2013">{{cite book|author=Juel, Connie|chapter=The Impact of Early School Experiences on Initial Reading|editor1=David K. Dickinson|editor2=Susan B. Neuman|title=Handbook of Early Literacy Research|chapter-url=https://books.google.com/books?id=_chXAQAAQBAJ&pg=PA421|year=2013|publisher=Guilford Publications|isbn=978-1-4625-1470-0|url-status=live|archive-url=https://web.archive.org/web/20170109162332/https://books.google.com/books?id=_chXAQAAQBAJ&pg=PA421|archive-date=9 January 2017|df=dmy-all}}</ref>{{rp|421}} Languages such as Spanish, Italian and Finnish primarily employ letter-sound correspondence—so-called "shallow" orthographies—which makes them easier to learn for people with dyslexia.<ref name="BrunswickMcDougall2010"/>{{rp|266}} [[Logograph]]ic writing systems, such as [[Chinese characters]], have extensive symbol use, and these also pose problems for dyslexic learners.<ref>{{cite journal|title = Annual Research Review: The nature and classification of reading disorders – a commentary on proposals for DSM-5|journal = Journal of Child Psychology and Psychiatry, and Allied Disciplines|date = 1 May 2012|pmc = 3492851|pmid = 22141434|pages = 593–607|volume = 53|issue = 5|doi = 10.1111/j.1469-7610.2011.02495.x|first1 = Margaret J|last1 = Snowling|first2 = Charles|last2 = Hulme}}</ref>