Background
Some patients with bipolar disorder (BD) demonstrate neuropsychological deficits even
when stable. However, it remains unclear whether these differ qualitatively from those
seen in schizophrenia (SZ).
Methods
We compared the nature and severity of cognitive deficits shown by 106 patients with
SZ and 66 patients with BD to 316 healthy adults (NC). All participants completed
a cognitive battery with 19 individual measures. After adjusting their test performance
for age, sex, race, education, and estimated premorbid IQ, we derived regression-based
T-scores for each measure and the six cognitive domains.
Results
Both patient groups performed significantly worse than NCs on most (BD) or all (SZ)
cognitive tests and domains. The resulting effect sizes ranged from .37 to 1.32 (mean
= .97) across tests for SZ patients and from .23 to .87 (mean = .59) for BD patients.
The Pearson correlation of these effect sizes was .71 (p < .001).
Conclusions
Patients with bipolar disorder suffer from cognitive deficits that are milder but
qualitatively similar to those of patients with schizophrenia. These findings support
the notion that schizophrenia and bipolar disorder show greater phenotypic similarity
in terms of the nature than severity of their neuropsychological deficits.
Key Words
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Article Info
Publication History
Published online: December 12, 2006
Accepted:
September 21,
2006
Received in revised form:
September 20,
2006
Received:
July 22,
2006
Identification
Copyright
© 2007 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
