Left-Handedness and Dyslexia Risk
Yes, left-handed people appear to have a modestly increased likelihood of being dyslexic, though the relationship is complex and not fully understood.
The Evidence
The association between left-handedness and dyslexia has been documented across multiple research studies, though the strength and nature of this relationship remains debated:
Key Findings from Research
Prevalence data shows an elevated rate of left-handedness among dyslexic populations. One Norwegian study of 734 children found a significant association between handedness and dyslexia, with handedness appearing to be the most important factor when examining the triad of dyslexia, left-handedness, and immune disorders 1. Specifically, this study found that 32% of dyslexic children with immune disorders were left-handed (P < .05), and 42.1% of left-handed children with immune disorders had dyslexia (P < .01).
Another study examining dyslexic children found an unusual frequency of 18% left-handed children in the dyslexic group compared to good readers, along with a high frequency of soft neurological signs in these left-handed dyslexic children 2.
Most recent neuroimaging evidence from 2025 provides contemporary support for this association. In a study of 282 healthy aging adults, non-right-handedness and male sex significantly predicted endorsed reading disability 3. This study found that individuals with reading disability showed decreased neural activity in left hemisphere regions critical for reading, with disruptions occurring in a network-specific manner that distinguished them from normal readers.
The Geschwind-Behan Hypothesis
Much of the historical interest in this association stems from the Geschwind-Behan hypothesis, which proposed that early developmental factors affecting the left hemisphere could result in both left-handedness and dyslexia. However, the evidence for this theory is mixed:
- One study of 87 dyslexics from 14 extended families found no elevation in left-handedness among dyslexics, though they did find elevated immune disorders 4
- Another study testing the hypothesis found weak support, with left-handed dyslexic boys showing some predicted patterns of hemispheric asymmetry but not others 5
Important Caveats
The association is not deterministic: Most left-handed people are not dyslexic, and most dyslexic individuals are right-handed. The relationship appears to be one of increased risk rather than causation.
Handedness patterns in language dominance: Approximately 70% of left-handed people lateralize language functions to the left hemisphere (same as all right-handed people), 15% have bilateral representation, and only 15% have right hemisphere language dominance 6. This means that left-handedness alone does not predict atypical brain organization for language.
Male sex is also a risk factor: The 2025 study found that both non-right-handedness AND male sex independently predicted reading disability 3, suggesting multiple demographic risk factors interact.
Clinical Implications
- Left-handedness should be considered as one of multiple risk factors for dyslexia, not a diagnostic criterion
- Screening for reading difficulties should not be based on handedness alone but should be part of routine developmental surveillance
- The presence of left-handedness in a child with reading concerns may warrant closer attention to phonological processing and reading development
- Early intervention remains critical regardless of handedness status
The relationship between left-handedness and dyslexia exists but is modest, complex, and likely reflects underlying neurodevelopmental variations rather than a simple causal pathway.