Impairment of verbal learning and memory and executive function in unaffected siblings of probands with bipolar disorder.
OBJECTIVE
Impairments in executive function and memory have been reported in relatives of patients with bipolar disorder, suggesting that they could be potential endophenotypes for genetic studies, but the findings are inconsistent. In this study, neuropsychological performance in unaffected siblings of probands with family loading for bipolar disorder is compared to that of individually matched healthy controls. We hypothesized that performance on tests of executive functions and memory would be impaired in unaffected siblings of probands with bipolar disorder compared to matched healthy controls.


METHODS
We evaluated 30 unaffected siblings of probands with bipolar I disorder and 30 individually matched healthy controls using tests of attention, executive function, and memory. Unaffected siblings and healthy control subjects did not differ with respect to gender, age, and years of education.


RESULTS
Unaffected siblings performed poorly on the Tower of London test (TOL), the Rey's auditory verbal learning test (RAVLT), and the Rey's complex figure test. In the multivariate analysis, significance was noted for the TOL, total number of moves (p = 0.007) and the RAVLT total learning score (p = 0.001).


CONCLUSIONS
Our study suggests that the deficits in verbal learning and memory and executive functions (planning) could be potential endophenotypes in bipolar disorder. These deficits are consistent with the proposed neurobiological model of bipolar disorder involving the frontotemporal and subcortical circuits. Future studies could couple cognitive and imaging strategies and genomics to identify neurocognitive endophenotypes in bipolar disorder.
Kulkarni
Sandip
S
Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, India.
Jain
Sanjeev
S
Janardhan Reddy
Y C
YC
Kumar
Keshav J
KJ
Kandavel
Thennarasu
T
D000328:Adult; D001714:Bipolar Disorder / Q000150:complications* / Q000235:genetics; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000150:complications* / Q000235:genetics; D005260:Female; D006801:Humans; D007859:Learning Disabilities / Q000150:complications* / Q000235:genetics; D008297:Male; D008569:Memory Disorders / Q000150:complications* / Q000235:genetics; D035781:Siblings; D014706:Verbal Learning; D055815:Young Adult