Dyslexia is a learning disorder that involves difficulty reading due to challenges recognizing speech sounds and learning how they relate to letters and words. There has been much debate over whether dyslexia is something you are born with or something you can develop later in life.
Quick Answers
- Research suggests dyslexia has a strong genetic component and runs in families, indicating some people are predisposed to developing it.
- However, dyslexia symptoms may not become apparent until a child starts learning to read, so it is often not diagnosed until the elementary school years.
- Some studies show brain abnormalities and cognitive differences in children as young as infancy who later develop dyslexia.
- While genetics play a role, environmental factors like trauma, brain injury, inadequate reading instruction, and socioeconomic disadvantages may also contribute to dyslexia risk.
- Most experts believe dyslexia is the result of both genetic and environmental influences rather than strictly innate or acquired.
Is dyslexia hereditary?
There is strong evidence that dyslexia runs in families. Studies show that 25-40% of children with dyslexia have a parent or sibling with the same disorder. The risk is higher if both parents have dyslexia. Researchers have identified some genes associated with dyslexia, such as DCDC2, KIAA0319, and DYX1C1. Having these genes does not guarantee a child will develop dyslexia, but indicates a genetic predisposition.
Twin studies
Twin studies have been instrumental in demonstrating the hereditary nature of dyslexia. Identical twins share 100% of their DNA, while fraternal twins share only 50% on average. When one identical twin has dyslexia, the other twin has a 75-100% chance of also having it. For fraternal twins, the likelihood is only 38-50%. This shows dyslexia is not purely environmental, but has a strong genetic influence.
Brain imaging
Brain imaging studies also provide evidence for the biological basis of dyslexia. Children and adults with dyslexia show less activation in regions linked to reading and phonological processing, even before receiving reading instruction. There are also anatomical brain differences present from birth in children who later develop dyslexia compared to non-dyslexic children.
Can dyslexia develop later in life?
While genetics play a key role, research does not support the view that dyslexia is solely an innate, unchangeable trait. There is evidence that environmental factors can also increase risk for dyslexia or trigger onset of symptoms later in life.
Reading instruction
There is debate around how much inadequate reading instruction contributes to reading struggles. Children with a genetic predisposition for dyslexia may not develop it with strong phonics intervention. However, poor instruction may trigger onset in those already at risk.
Trauma/injury
Neurological trauma or injury has been linked to acquired dyslexia. Damage to left hemisphere brain regions critical for reading can occur through events like strokes, tumors, head injuries, or neurodegenerative diseases. This damage leads to the sudden emergence of dyslexia-like symptoms in both children and adults with no prior reading disabilities.
Socioeconomic status
Children from lower socioeconomic backgrounds are more likely to exhibit reading delays. Factors like limited access to books, less reading time with parents, increased stress, and attendance at underfunded schools may contribute to dyslexia risk.
Critical periods
There appear to be critical periods in childhood development where the brain is especially primed to develop linguistic skills. Disruptions to these stages through social deprivation, trauma, or abnormalities in brain maturation may impact dyslexia risk.
- Newborns: Sound discrimination abilities important for language acquisition emerge.
- Infants: Phonemic awareness and grapheme-phoneme correspondences begin forming.
- Ages 5-10: Rapid period of reading and writing skill development.
Interventions during these periods could potentially reduce likelihood of dyslexia in genetically predisposed children.
Is there an age limit for developing dyslexia?
Most cases of dyslexia emerge when children first start learning to read, during ages 5-7. However, new research shows dyslexia can manifest even into adulthood. Causes include:
- Compensation – Adults who developed coping mechanisms as children may deteriorate when demands increase.
- New onset – Late-emerging cases likely reflect interaction of genetics and environment over time.
- Brain injury – Trauma can damage areas key for reading skills.
While there is no cut-off age, developmental dyslexia diagnoses typically occur before age 13. Cases emerging later usually involve external causes like brain injury.
Conclusion
In summary, dyslexia appears to arise from an intricate mix of genetic vulnerabilities and environmental triggers. While certain individuals may be born with a predisposition, dyslexia characteristics often do not become apparent until reading instruction begins. Even in adulthood, new cases can emerge due to brain trauma, increasing cognitive demands, or gradual effects of genetics and environment. These findings suggest dyslexia may be best viewed on a continuum – as both innate and acquired depending on the individual profile and trajectory. Understanding the complex causes is key for developing effective early interventions and treatment approaches.