Persistent Cognitive Dysfunctions in Bipolar I Disorder and Schizophrenic Patients: A 3-Year Follow-Up Study

Abstract

Background: Neurocognitive impairment has consistently been considered a central and stable feature in schizophrenia. As this possibility has been far less studied in bipolar disorder, we aimed to prospectively investigate the stability and specificity of cognitive performance in bipolar disorder compared to schizophrenia. Methods: Fifteen DSM-IV bipolar type I patients and 15 schizophrenic patients were assessed twice with a comprehensive neuropsychological battery and the Positive and Negative Syndrome Scale over a 3-year follow-up. The cognitive performance of the groups was compared at baseline and 3 years later as a mean with that of 26 healthy volunteers. Endpoint and baseline assessments were also compared for each patient group in order to evaluate the stability of cognitive impairment. Results: At both time points, bipolar and schizophrenic patients showed significant deficits on most of the cognitive tasks compared to healthy subjects. Overall, the cross-sectional cognitive profile was similar for both patient groups. Moreover, after controlling for age and length of illness, the two groups’ cognitive function did not differ over time in any test. With the exception of the Stroop color-word interference task, performance at baseline for each test but neither length of illness nor diagnostic category predicted the endpoint performance. Conclusion: This preliminary study suggests that cognitive impairment is also mainly stable over time in bipolar I disorder and thus not specific to schizophrenia.

Cognitive Impairment in Schizophrenia and Affective Psychoses: Implications for DSM-V Criteria and Beyond

“…[9][10][11] While only a few longitudinal studies have examined cognitive deficits in BD, recent evidence suggests that cognitive impairment might also be stable over the long term. 28,29 These results, as in schizophrenia, suggest that cognitive impairment is not simply a by-product of other symptom domains in BD. The findings of recent studies in unaffected first-degree relatives of BD also suggest that cognitive impairment might be a trait-related feature of BD.…”

Do Cognitive Complaints in Euthymic Bipolar Patients Reflect Objective Cognitive Impairment?

“…Bipolar disorder is associated with global rather than specific patterns of impairment that are similar to those seen in schizophrenia and sometimes reported in unipolar disorder [30, 31]. …”

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“…Los déficits neurocognitivos se vinculan con alteraciones funcionales. Estudios de seguimiento sugieren que estos tienden a ser permanentes en sujetos bipolares 36,38,39 . Este inferior desempeño se asoció a un peor curso de la enfermedad junto a mayor sintomatología, mayor número de episodios, hospitalizaciones y compromiso de las habilidades sociales 40 .…”