Study says left-handed people more likely to have psychotic disorders

Left-handed writing (stock)

Yale researcher Jadon Webb and his colleagues have found that people with mental illnesses, specifically psychotic disorders like schizophrenia, are more likely to be left-handed than are those with mood disorders like bipolar disorder or depression.

The study

Published in the fourth quarter issue of the journal SAGE Open, the study looked at patients with diagnosed mental disorders and compared their dominant sides (hands). The general population has about 10 percent of people in the U.S. being left-handed. The researchers found that about 11 percent of those with diagnosed mood disorders were left-handed, statistically consistent with the general population.

But Webb and his team found that 40 percent of those with schizophrenia and shizoaffective disorder are left-handed. This, says Webb, who is a Yale Child Study Center research fellow with interest in biomarkers for psychosis, "can hopefully enable us to identify and differentiate mental disorders earlier" through the use of biomarkers like being left-handed.

Other surprising findings

The study looked at 107 individuals from a public outpatient psychiatric clinic with diagnosed mental disorders. Other findings included the fact that white left-handers are more likely to be psychotic than are left-handed black people. The study itself was conducted with only one question asked of the patient when visiting: "What hand do you write with?" The rest of the data came from patient medical records released to the study.

Webb said that this simple approach allowed the study to be inclusive and non-intrusive for the patient during a normally-scheduled visit.

The study can be found here.


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