Neurocognitive profiles in bipolar I and bipolar II disorder: differences in pattern and magnitude of dysfunction

Authors


  • The authors of this paper do not have any commercial associations that might pose a conflict of interest in connection with this manuscript.

Corresponding author: Carmen Simonsen, Department of Psychiatry, Ulleval University Hospital, 0407 Oslo, Norway. Fax: +47 23 02 73 33;
e-mail: c.e.simonsen@medisin.uio.no

Abstract

Objectives:  Studies on neurocognitive functioning in bipolar disorder, reporting deficits in memory, attention, and executive functioning, have primarily focused on bipolar I disorder. The aim of this study was to examine whether patients with bipolar I and bipolar II disorder have different neurocognitive profiles.

Methods:  Forty-two patients with bipolar I disorder, 31 patients with bipolar II and 124 healthy controls, from a large ongoing study on psychotic disorders, were included. Neurocognitive function was measured with a comprehensive neuropsychological test battery.

Results:  The bipolar I group performed significantly poorer than the healthy control group and the bipolar II group on all measures of memory. Compared with the control group, the bipolar I group also had significantly reduced performance on most measures of attention and executive functioning, while the bipolar II group only had a significantly reduced performance on a subset of these measures. On average, 24% of the bipolar I group had clinically significant cognitive impairment (≤1.5 SD below the control group mean) across measures, compared with 13% of the bipolar II group.

Conclusions:  Patients with bipolar I and bipolar II disorder in this study have different neurocognitive profiles. Bipolar I patients have more widespread cognitive dysfunction both in pattern and magnitude, and a higher proportion has clinically significant cognitive impairments compared with patients with bipolar II. This may suggest neurobiological differences between the two bipolar subgroups.

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