New Study Reveals Why Lefties Are More Common in Autism and Dyslexia
A major international study published in Psychological Bulletin has confirmed a strong link between atypical handedness — being left-handed or ambidextrous — and neurodevelopmental disorders such as autism, dyslexia, and schizophrenia. Researchers analyzed data from over 200,000 individuals and found that these conditions, which typically emerge early in life and often involve language difficulties, are significantly more common among non-right-handed people. The findings suggest that handedness and language-related disorders may share common roots in early brain development. This research not only sheds light on why hand preference varies in certain clinical populations but also highlights how the brain’s asymmetry influences cognition, communication, and mental health.
Who Conducted the Study and What They Found
According to Neuroscience News, the study was carried out by a team of scientists from Ruhr University Bochum in Germany, Medical School Hamburg, Radboud University in the Netherlands, and the National and Kapodistrian University of Athens. Key researchers included Dr. Julian Packheiser and Professor Sebastian Ocklenburg, both experts in neuroscience and psychology.
Instead of running new experiments, the team used a method called a second-order meta-analysis. This means they analyzed the results of other meta-analyses — studies that already combined many individual research papers. In total, they reviewed 402 datasets covering more than 202,000 people. This allowed them to look for larger patterns across multiple mental and developmental disorders, especially focusing on when the disorders begin and whether they involve problems with language.
They published their findings on May 2, 2025, in Psychological Bulletin, a well-respected scientific journal (https://doi.org/10.1037/bul0000471).
What’s New About This Research
Previous research has examined hand preference in individual disorders such as schizophrenia or dyslexia, with mixed results — some studies reported higher rates of left-handedness, while others found no significant differences. What makes this new study distinctive is its scale and analytical depth. It is the first large-scale second-order meta-analysis to compare data across multiple disorders by focusing not only on diagnoses but also on the timing of symptom onset and the presence of language-related difficulties. This approach allowed researchers to uncover broader patterns that may have been missed in earlier, diagnosis-specific studies.
By comparing so many different datasets, the researchers could identify a clear pattern: conditions that begin in early life and involve language difficulties are much more likely to be associated with left- or mixed-handedness.
Key Findings: Five Important Takeaways
1. Higher rates of left- or mixed-handedness in early-onset disorders. People with autism, dyslexia, and schizophrenia were more likely to be left-handed or ambidextrous than people without these disorders.
Example: A child with dyslexia may also prefer using their left hand or switch between hands when writing or eating.
2. The earlier the disorder appears, the stronger the link. The connection between hand preference and a disorder was strongest in those that begin during early childhood.
Example: Autism, which often shows signs before age 3, had a stronger association than conditions that start later in life.
3. Language symptoms play a key role. The disorders most closely linked to left-handedness involved some kind of language difficulty, such as trouble reading (dyslexia), communicating (autism), or organizing thoughts (schizophrenia).
Example: A child who speaks with delays and often switches hands while writing may show brain patterns linked to both language difficulties and mixed-handedness.
4. No link with later-onset mental health issues. Conditions like depression, which typically start in adulthood and don’t usually involve language problems, showed no connection to hand preference.
Example: An adult diagnosed with depression in their 30s is no more likely to be left-handed than the general population.
5. Shared early brain development processes. Both handedness and language abilities develop during early brain formation. If this process is disrupted — by genetics or environmental factors — it can lead to differences in both areas.
Example: A baby born with subtle brain differences might later show both language delays and a tendency to use the left hand.
How It Relates to the Brain and Thinking Abilities
Handedness is more than a matter of preference — it reflects how the brain is structured and how its functions are distributed between the two hemispheres. In most right-handed individuals, language processing is strongly concentrated in the left hemisphere. However, in left-handed or ambidextrous people, brain organization tends to be more varied. Their language centers may be located in the right hemisphere, shared across both hemispheres, or arranged in less typical ways.
This variation can influence not only motor coordination but also cognitive abilities such as language acquisition, memory, attention, spatial awareness, and emotional processing. When the typical patterns of brain lateralization are altered early in development, it can affect how neural networks form — potentially leading to both strengths and difficulties in areas like reading, verbal communication, or executive function.
The study’s authors suggest that atypical handedness may serve as an external marker of these internal neurological differences. In conditions like autism and dyslexia, where language and communication are often affected, such markers could offer important clues about the underlying brain architecture and its role in cognitive development.
What These Findings Could Mean for Healthcare, Education, and Society
The results of this large-scale analysis offer more than just scientific insight — they could shape how doctors, teachers, and society as a whole approach early brain development and neurodiversity.
From a research perspective, the study supports a growing movement in neuroscience to focus on what different conditions have in common, rather than treating each diagnosis as entirely separate. By showing that early-onset disorders involving language difficulties often share brain development patterns with left- or mixed-handedness, the findings promote a broader, symptom-based understanding of mental health and neurodevelopment.
For healthcare professionals, especially those working with children, this information may aid in earlier identification of developmental challenges. A child who shows both unclear hand preference and early speech delays, for example, might benefit from closer monitoring and support during critical stages of learning.
In education, teachers and school psychologists may use these insights to better understand students who struggle with reading, language, or social communication — especially when paired with unusual hand use. This could lead to earlier, more effective intervention strategies tailored to individual learning profiles.
Finally, the study offers a broader perspective on how traits like handedness relate to individual differences in brain development. Rather than being unusual, variations in hand preference may reflect natural patterns in how cognitive functions are distributed in the brain. Understanding these patterns can improve how developmental differences are identified and supported, especially in educational and clinical settings.
Conclusion: What Hand Preference Reveals About Early Brain Development
The new findings emphasize that hand preference — often seen as a simple personal trait — can provide valuable insights into how the brain forms in early life. Left- and mixed-handedness are significantly more common among people with early-onset neurodevelopmental conditions that involve language difficulties, such as autism, dyslexia, and schizophrenia.
Researchers believe this is not a coincidence, but rather a reflection of shared developmental pathways in the brain. While atypical handedness alone is not a cause for concern, its presence alongside other symptoms may serve as an early indicator for further evaluation or support.
Ultimately, the study underscores how closely connected physical traits like handedness are to brain structure and cognitive functioning. It highlights the importance of early brain development — a period when the foundations of language, memory, attention, and emotional regulation are being formed. These findings reinforce the value of stimulating and supporting children’s cognitive growth from an early age. Brain training, language-rich environments, and tailored learning strategies can all play a key role in helping each child build strong mental skills and adaptive learning pathways.
