Researchers have long studied the connections between hand dominance and different aspects of the human brain. A new study out today in SAGE¹ Open finds that among those with mental illnesses, left-handers are more likely to suffer from psychotic disorders³ such as schizophrenia（精神分裂症） than mood disorders. "Our results show a strikingly higher prevalence of left-handedness among patients presenting with psychotic disorders such as schizophrenia and schizoaffective disorder², compared to patients presenting for mood symptoms such as depression or bipolar disorder," wrote the authors.

 

Authors Jadon R. Webb, et. al examined 107 individuals from a public psychiatric clinic seeking treatment in an urban, low-income community and determined⁴ the frequency of left-handedness within the group of patients identified with different types of mental disorders. They found that 11% of those diagnosed with mood disorders such as depression and bipolar disorder were left-handed, which is similar to the rate in the general population, however, 40% of those with schizophrenia or schizoaffective（情感性分裂的） disorder were left-handed.

 

The authors discussed additional factors that might be tied to the connection between schizophrenia and left-handedness such the variation of brain lateralization, scholastic⁵ achievement or race.

 

"Our own data showed that whites with psychotic illness were more likely to be left-handed than black patients," the authors wrote. "Even after controlling for this, however, a large difference between psychotic and mood disorder patients remained."

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