Left-handedness and schizophrenia

Lefties have it tough, and not just when they have to use right-handed scissors. The 10 percent of the population who are left-handed are born earlier, suffer more fatal accidents, and have higher rates of epilepsy and autism. Some studies have found that there is also more left-handedness in those diagnosed with schizophrenia; others have suggested that there might be a link to mood disorders—bipolar disorder and depression. A new Yale study offers evidence for the first hypothesis, but none for the second.

Jadon Webb, a child and adolescent psychiatry fellow at the Yale Child Study Center, and his colleagues studied 107 inner-city psychiatric clinic patients with psychotic or mood disorders, asking  which hand they normally preferred to write with. Nearly every patient answered, leading the team to believe they now have a more accurate picture of a community that can be difficult to research.

Eleven percent of the patients with mood disorders reported preferring the left hand. But among patients with schizophrenia or schizoaffective disorder, the number was 40 percent. Perhaps due to the relative simplicity of the study, as well as traits this urban outpatient group may have had in common, the number was higher than results in previous studies, which ranged up to 31 percent.

Webb’s stark finding, if confirmed in larger studies, lends urgency to the need to figure out the underlying link between schizophrenia and left-handedness. That’s in part because psychosis, if spotted early, can be delayed or prevented. “Left-handedness may be one easy-to-measure sign that, when combined with other measures, may help point to who is most at risk,” says Webb.