Siblings of bipolar patients show reduced executive function and memory
MedWire News: The unaffected siblings of patients with bipolar disorder show deficits in executive functions and memory relative to mentally healthy individuals without a family history of the condition, researchers have found.
"These deficits are consistent with the proposed neurobiological model of bipolar disorder involving the frontotemporal and subcortical circuits," and suggest potential endophenotypes for genetic studies, say YC Janardhan Reddy (National Institute of Mental Health and Neurosciences, Bangalore, India) and team.
Reddy and team compared neuropsychological performance between 30 unaffected siblings of BD patients and 30 mentally healthy controls without such a family history who were matched for age, gender, and education level.
All of the participants, who were aged between 18 and 45 years, underwent a battery of tests to assess attention, executive functions, and memory.
The researchers found no significant differences between the groups on tests of attention.
However, with regard to executive functions, unaffected siblings performed significantly worse than controls on the total number of moves item of the Tower of London test, which assesses planning ability, with scores of 80.43 versus 63.63.
Unaffected siblings also performed significantly worse than controls on Rey's auditory verbal learning test, with total learning scores of 53.70 versus 61.60.
In addition, unaffected siblings had poorer performances than controls on two items of Rey's Complex Figure Test, which assesses recall, but the differences did not reach significance.
Reddy and team conclude in the journal Bipolar Disorders: "Our study of the unaffected siblings of bipolar disorder probands suggests that impairments in verbal learning and memory and planning are potential endophenotype markers for bipolar disorder."
They add: "Studies involving larger sample sizes of unaffected relatives may help identify the cognitive endophenotypes that are robust."
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By Mark Cowen