Differences between bipolar I and II patients regarding neurocognitive performance

Background

Persistent impairments in neurocognitive function have been described in patients with bipolar disorder whose disease is in remission. So far, no studies have been performed to identify the specific differences regarding neuropsychological performance when bipolar I and bipolar II subtypes are compared.

Materials and methods

A sample of 71 euthymic bipolar patients (38 bipolar I, 33 bipolar II), were included in the study. Euthymia was defined by a score of 6 or less at the Young Mania Rating Scale, and a score of 8 or less at the Hamilton Depression Rating Scale, for at least six months),. The bipolar I and II patients were compared on several clinical and neuropsychological variables and the two groups were contrasted with 35 healthy controls on cognitive performance.

Results

The two groups showed significant deficits in most cognitive tasks compared to healthy controls. After controlling for age, bipolar I patients performed worse than bipolar II patients in all neurocognitive measures. However, the bipolar II group showed a trend towards a higher number of perseverative errors in the Wisconsin Card Sorting Test compared to the bipolar I group, but differences did not reach statistical significance.

Discussion

Cognitive impairment exists in both subtypes of bipolar disorder, although it is most evident in the bipolar I group. Bipolar II patients seem to show an intermediate profile regarding neurocognitive performance between bipolar I and healthy controls.