Summary: A new second-order meta-analysis finds a clear association between early-onset neurodevelopmental disorders that include language-related symptoms and increased rates of left- and mixed-handedness. Conditions such as dyslexia, autism spectrum disorders, and schizophrenia show notably higher proportions of non-right-handed individuals, while later-onset disorders like depression do not exhibit this pattern.
The authors conclude that this overlap most likely reflects shared processes in early brain development, since both hand preference and language lateralization are established during prenatal and early postnatal stages. The timing and nature of developmental disruptions appear to influence handedness patterns among affected individuals.
Key Facts:
- Increased left/mixed-handedness: Dyslexia, autism, and schizophrenia are associated with significantly higher rates of left- and mixed-handedness compared with control groups.
- Early manifestation is critical: The link is strongest for disorders that appear early in life and involve language or communication symptoms.
- No consistent link in later disorders: Conditions with later average onset, such as major depressive disorder, show no reliable association with atypical hand preference.
Source: RUB (Ruhr University Bochum)
Linguistic symptoms and early onset: higher rates of left- or mixed-handedness in certain disorders
Clinicians and researchers have long observed that left- and mixed-handedness occur more frequently in people with some neurological and neurodevelopmental conditions, particularly those that affect communication and language. To clarify these observations, an international team from Bochum, Hamburg, Nijmegen and Athens reanalyzed and integrated previously published meta-analyses from a new, symptom- and development-focused perspective.
Their goal was to determine overarching patterns across diagnoses and to evaluate whether factors such as age of onset and the presence of language-related symptoms moderate the relationship between hand preference and psychopathology.
Published in Psychological Bulletin on May 2, 2025, the study reports that atypical hand preference (non-right, left, or mixed) is significantly more common among clinical cases than among controls, and that this effect varies systematically across diagnostic categories.
Symptoms and developmental timing as the starting point
The research team began from the hypothesis that handedness would be associated mainly with disorders involving language symptoms and with conditions that manifest early in life. Handedness and language lateralization are both established during early brain development, so disorders that arise during or shortly after these periods are the most plausible candidates for shared developmental influences.
“Language, like handedness, is strongly lateralized in the brain, which suggests a common developmental substrate,” explains Dr. Julian Packheiser from the Institute of Cognitive Neuroscience at Ruhr University Bochum. Professor Sebastian Ocklenburg from the Medical School Hamburg adds that both initial hypotheses—an association with language-related symptoms and with early onset—were supported by the data.
For example, dyslexia (a developmental reading disorder) showed a statistically significant excess of left- and mixed-handed individuals compared with control samples. Autism spectrum disorders, which often include communication and social-communication impairments, and schizophrenia, which can involve disordered language processing and auditory hallucinations, were also associated with elevated rates of atypical hand preference.
Handedness across neurodevelopmental and psychiatric disorders
Consistent with the developmental hypothesis, the strength of the association between atypical handedness and clinical status correlated with how early symptoms typically appear. Disorders with early onset showed the strongest accumulation of left- and mixed-handedness, whereas later-onset conditions did not.
“We did not find a meaningful connection for depression, which on average emerges much later in adulthood,” notes Dr. Packheiser. This supports the interpretation that overlapping early developmental processes influence both hand preference and vulnerability to certain neurodevelopmental conditions.
About this research on handedness and neurodevelopmental disorders
Author: Julian Packheiser
Source: RUB (Ruhr University Bochum)
Contact: Julian Packheiser – RUB
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Handedness in Mental and Neurodevelopmental Disorders: A Systematic Review and Second-Order Meta-Analysis” by Julian Packheiser et al., Psychological Bulletin.
Abstract
Handedness in Mental and Neurodevelopmental Disorders: A Systematic Review and Second-Order Meta-Analysis
Over the past decade, numerous meta-analyses have examined hand preference across various mental and neurodevelopmental disorders. While some conditions, such as schizophrenia, consistently show elevated rates of atypical hand preference, others, including depression, do not. To detect generalizable patterns and to estimate moderator effects beyond diagnosis-specific findings, the authors performed a higher-level synthesis by reviewing, updating, and reanalyzing existing meta-analytic data.
The second-order meta-analysis incorporated 402 datasets comprising a total of 202,434 individuals. Across studies, atypical hand preference was significantly more frequent in clinical cases than in controls: non-right preference odds ratio (OR) = 1.46 (95% CI: 1.35–1.59); left-hand preference OR = 1.34 (95% CI: 1.22–1.48); mixed preference OR = 1.63 (95% CI: 1.38–1.93). Results varied by diagnosis, with schizophrenia showing consistently elevated odds (non-right OR = 1.50, left OR = 1.37, mixed OR = 1.70).
Moderator analyses indicated that neurodevelopmental disorders, non-neurodevelopmental conditions with an early age of onset, and disorders that include language-related symptoms are all associated with higher rates of atypical hand preference. These findings suggest that the relationship between hand preference and clinical conditions is best interpreted through a transdiagnostic, developmental, and symptom-focused lens.