A new study from Ruhr University Bochum suggests a link between left-handedness or mixed-handedness and neurological disorders that manifest early in life and involve linguistic symptoms.
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Researchers re-evaluated existing meta-analyses, hypothesizing that handedness could be associated with disorders affecting language, which, like handedness, is localized in one side of the brain. They also suspected a link with diseases occurring early in life, as handedness is determined early in development.
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The study found that left-handedness and mixed-handedness are more common in individuals with dyslexia, autism, and schizophrenia. "Both hypotheses have been confirmed," says Professor Sebastian Ocklenburg from the Medical School Hamburg.
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The research indicates that the earlier the symptoms of a disorder manifest, the more frequent the occurrence of left and mixed-handedness. "In people with depression, which on average occurs around the age of 30, we couldn't show any connection," points out Julian Packheiser.
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The researchers propose that handedness and certain neurodevelopmental disorders are influenced by overlapping processes in early brain development. This suggests a shared developmental pathway for both.