Handedness Linked to Neurodevelopmental Disorders: New Meta-Analysis

A new meta-analysis reveals connections between handedness and mental and neurodevelopmental disorders. The study, published in the Psychological Bulletin, explores left- and mixed-handedness among individuals with neurological conditions. Researchers from Ruhr University Bochum and the Medical School Hamburg led the study. The study focuses on the idea that handedness and language are lateralized functions in the brain. Right-handedness is most common, with about 90% of people favoring the right hand. Left- and mixed-handedness are more frequent in people with certain neurological disorders. The research team re-assessed existing meta-analyses, focusing on disorders connected to linguistic processing. Dr. Julian Packheiser stated, "We hypothesized that the co-occurrence of atypical handedness with language-related disorders might reflect shared underlying neurodevelopmental mechanisms." The study emphasized the temporal emergence of symptoms alongside handedness patterns. The findings showed that dyslexia had a statistically significant elevated incidence of left- and mixed-handedness. Autism spectrum disorder (ASD) and schizophrenia also demonstrated a higher prevalence of non-right-handed traits. This highlights the developmental convergence of hemispheric specialization for language and motor functions. Early-onset neurodevelopmental disorders displayed a marked congruence with handedness variations. Professor Sebastian Ocklenburg noted, "This temporal gradient suggests that atypical handedness may serve as a behavioral biomarker reflective of altered early neurodevelopmental processes." Conditions appearing later in life, like major depressive disorder, showed little to no correlation. The findings suggest that cerebral lateralization is intricately implicated in the pathophysiology of developmental disorders. Handedness may offer an accessible way to probe deeper into atypical brain organization. Lateralization emerges early during prenatal development, influenced by genetics, epigenetics, and environmental factors. Recognizing handedness patterns could enhance early identification of at-risk individuals. It also opens avenues for tailored interventions that acknowledge the neural underpinnings of lateralized brain dysfunction. The absence of association between left- or mixed-handedness and affective disorders underscores the specificity of neural developmental pathways involved. The meta-analysis positions handedness as a testament to the interplay between early brain development and neurodevelopmental disorders. The translational potential of these insights underscores the need to incorporate lateralization metrics in clinical assessment and research. This marks a significant stride toward understanding the biological substrates of cognitive diversity.