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Left-Handed Patients More Likely to Have Psychotic Disorders

In a multi- centered joint study published in the October-December 2013 issue of SAGE Open, lead author Jadon Webb, MD of the Yale Child Study Center reported that the prevalence of left-handedness among patients with psychotic illnesses like schizophrenia or schizoaffective disorder reached 40%. By comparison, those with depression were noted to have normal average levels of 10%. The researchers noted that previous studies have proposed that the asymmetry of the brain’s left and right hemispheres may cause the correlation, as “variations in development of this asymmetry are suspected to contribute to the pathogenesis of schizophrenia…Finding biomarkers such as this can hopefully enable us to identify and differentiate mental disorders earlier, and perhaps one day tailor treatment in more effective ways,” Webb concluded.

According to Dr Levinson, “These results are fascinating–especially since they escaped prior attention and validation despite years of intensive schizophrenia research and a huge 4/1 readily observable difference. However, left-handedness was determined only by patients reporting which hand they wrote with. But there was a clear and significant distinction between those with schizophrenia and depression, clearly indicating important differences using this simple determination of left handedness and using depression as another control group.

I remain a little cautious since personally debunking many prior studies indicating a higher incidence of left-handedness and then mixed-handedness in dyslexia. These latter incorrect results were biased by the mistaken conviction that dyslexia was a language disorder caused by incomplete cerebral dominance which was then reasoned and found to cause mixed lateral dominance or decreased right handedness. So researchers found exactly what they expected, a phenomenon I always find suspicious. ‘Placebo statistics’ must occur as frequently as placebo improvements, and for similar psychological reasons.”

About Harold Levinson, M.D.

Formerly Clinical Associate Professor of Psychiatry at New York University Medical Center, Dr. Harold Levinson is currently Director of the Levinson Medical Center for Learning Disabilities  in Great Neck, Long Island, New York. He is a well known neuropsychiatrist, clinical researcher and author. His “highly original” research into the cerebellar-vestibular (inner-ear) origins and treatment of dyslexia and related learning, attention-deficit/hyperactivity and anxiety or phobic disorders has evolved over the past four decades. Initially supported by Nobel Laureate Sir John Eccles and other outstanding cerebellar neurophysiologists and inner-ear scientists, Levinson’s research has more recently been independently validated worldwide by highly sophisticated neuroimaging brain studies.

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Photo Courtesy of Ohmega1982/