Patients with bipolar disorder are around twice as likely to be non-righthanded as mentally healthy individuals, study results show.
Furthermore, this difference in non-righthandedness rates between BD patients and those without the mood disorder is even more pronounced among adolescents, report Hilary Blumberg (Yale School of Medicine, New Haven, Connecticut, USA) and team.
The findings, published in Bipolar Disorders, "may support previous studies suggesting disruptions in the development of hemispheric connections and specialization in BD," comment the authors.
"We speculate that such disruptions may contribute to the hemispherically lateralized abnormalities associated with acute mood states of the disorder, such as the association between right frontotemporal abnormalities and mania," they add.
The team studied 155 adolescents (aged 13-21 years, n=40) and adults (aged 22-64 years, n=115) with BD and 179 adolescent (n=87) and adult (n=92) controls without an Axis I psychiatric disorder or a family history of mood or psychotic disorders.
Of the participants with BD, 48% were euthymic, 26% depressed, and 26% were in a manic/hypomanic or mixed state at the time of the study.
All of the participants were assessed for non-righthandedness through self-report and scores on the 10-item Edinburgh Handedness Inventory (EDI), with lower scores indicating a more dominant left hand and higher scores indicating a more dominant right hand.
The researchers found that, overall, BD patients were significantly more likely to be non-right-handed than controls, at 15.4% versus 7.3%.
This difference was even greater in adolescent participants, with 20.0% of BD patients being non-right-handed compared with 5.7% of controls.
The researchers note that non-righthandedness was not associated with mood state or gender in the BD patients.
Blumberg et al conclude: "Future studies that investigate mechanisms that contribute to increased non-righthandedness and associated neural circuitry in BD, especially those related to hemispheric specialization, may provide insights into risk factors for the development of BD."
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