NEUROPSYCHOLOGICAL FUNCTIONING IN BIPOLAR DISORDER AND SCHIZOPHRENIA
Biol Psychiatry. 2006 Dec 8; [Epub ahead of print]
Schretlen DJ, Cascella NG, Meyer SM, Kingery LR, Testa SM, Munro CA, Pulver AE, Rivkin P, Rao VA, Diaz-Asper CM, Dickerson FB, Yolken RH, Pearlson GD.
Department of Psychiatry and Behavioral Sciences; Department of Radiology and Radiological Science.
ABSTRACT:
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 wit 19 individuals 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.