Cognitive functions in stable schizophrenia & euthymic state of bipolar disorder

Background & objectives: Some cognitive deficits in schizophrenia and bipolar disorders persist after the subsidence of active symptoms. We carried out this study to assess and compare the cognitive functioning of patients with stable schizophrenia and bipolar disorder. Methods: Fifteen each of stable maintained schizophrenic patients and euthymic bipolar-I patients attending outpatient clinic in a tertiary care psychiatric hospital in north India were included in the study as also equal number of age and education matched control subjects. Cognitive assessments were done using Wisconsin's Card Sorting Test (WCST), Spatial Working Memory Test (SWMT) and Continuous Performance Test (CPT). Results: Stable schizophrenia patients performed poorly on all the neurocognitive parameters as compared to both controls and bipolar euthymic patients. Euthymic bipolar patients showed significant difference on executive functions with normal controls. Patterns of cognitive disturbances in tasks of executive function are similar in both groups but are quantitatively more marked in schizophrenia. Interpretation & conclusions: Our results showed that stable schizophrenia patients performed significantly worse on cognitive measures than patients of euthymic bipolar disorder which was consistent with their poorer functional outcome. The results further indicated that stable schizophrenia and euthymic bipolar disorders may be distinguished qualitatively in neuropsychological terms with different profiles of cognitive impairment.