Scientists have revealed the key causes of dyslexia — and how it may shrink parts of the brain.
The learning difficulty, which causes sufferers to frequently spell and read words wrong, is known to run in families.
But scientists in the Netherlands have now pinpointed the exact DNA mutations that could be to blame for the problem — as well as the specific impact on the structure of the brain.
Dyslexia is partly influenced by genes and can be inherited, explained study author and neurogenetics researcher Sourena Soheili-Nezhad.
‘Yet, dyslexia is a complex trait, which cannot be explained by changes in a single brain region or a single gene,’ he added.
‘Studying exactly which genes affect which brain networks can help to understand how cognitive functions develop differently in this learning difficulty.’
In the study, published in the journal Science Advances, researchers used data from more than a million people collected by 23andMe, a company that sells at-home DNA testing kits.
This data revealed the genetic variants that increase the chance of a person having dyslexia — which affects some one in 10 Brits.
Researchers then used information extracted from the UK Biobank — a collection of health data from 30,000 people, including medical imaging and DNA mutations — to look for similarities in the brain scans of people with the previously identified genetic variant.
Researchers found those with the telltale genetic characteristics had a lower brain volume in areas of the brain involved with movement coordination and processing of speech sounds.
They also found above-average brain volume in the part of the brain responsible for vision.
A reduced amount of white matter, deeper tissue in the brain that contains nerve fibres, was also associated with dyslexia.
‘Although our study used data from adults, some of the changes probably relate to altered development of the brain during early stages of life, for example in the foetus or during infancy, which then remain stable across the lifetime,’ said genomics researcher Clyde Francks, who also worked on the study.
‘Other changes might reflect responses of the brain to decades of altered behaviour in people with higher genetic disposition to dyslexia.
‘For example, years of avoiding reading in personal and professional life might impact the brain’s visual system.’
However, the study authors say future research should focus on data from children instead of adults to track brain changes in development that are associated with causing dyslexia.
‘Understanding the brain basis of dyslexia could also possibly help to achieve earlier diagnosis and educational intervention in the future, with more targeted strategies suited to the profiles of individual children’, Soheili-Nezhad added.
Intelligence is not affected by dyslexia — but people with the learning difficulty can struggle in school unless offered additional support.
Dyslexia is tricky to diagnose early as some signs, like making frequent spelling or pronunciation mistakes, occur normally as children learn to read and write.
Most children with the learning difficulty are only spotted in primary school but some people with the condition are missed until well into adulthood.
The NHS suggests that parents concerned about their child’s reading and writing should talk to their teacher first, then consider seeking advice from a GP.
It adds that adults can arrange for an assessment with the British Dyslexia Association.
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