Neuropsychological functions in patients with bipolar I and bipolar II disorder.
The literature reports persistent cognitive impairments in patients with bipolar disorder even after prolonged remission. However, a majority of studies have focused only on bipolar I disorder (BP-I), primarily because bipolar II disorder (BP-II) is often underdiagnosed or misdiagnosed. More attention should be paid to the differences between BP-I and BP-II, especially the aspects of neuropsychological functioning. We examined the different neuropsychological functions in BP-I and BP-II patients and compared them with those of healthy controls.


METHODS
The study included 67 patients with interepisode bipolar disorder (BP-I: n = 30; BP-II: n = 37) and 22 healthy controls compared using a battery of neuropsychological tests that assessed memory, psychomotor speed, and certain aspects of frontal executive function.


RESULTS
The BP-I group performed poorly on verbal memory, psychomotor speed, and executive function compared to the BP-II and control groups. Both bipolar groups performed significantly less well than the control group on measures of working memory and psychomotor speed, while the BP-II group showed an intermediate level of performance in psychomotor speed compared to the BP-I and control groups. There was no difference between the groups on visual memory.


CONCLUSIONS
BP-I was characterized by reduced performance in verbal memory, working memory, psychomotor speed, and executive function, while BP-II patients showed a reduction only in working memory and psychomotor speed. Cognitive impairment existed in both subtypes of bipolar disorder, and was greater in BP-I patients. Rehabilitation interventions should take into account potential cognitive differences between these bipolar subtypes.
Hsiao
Yih-Lynn
YL
Institute of Behavioral Medicine, National Cheng Kung University Hospital, 138 Sheng-Li Road, Tainan 70428, Taiwan, ROC.
Wu
Yi-Syuan
YS
Wu
Jo Yung-Wei
JY
Hsu
Min-Hsien
MH
Chen
Hui-Chun
HC
Lee
Sheng-Yu
SY
Lee
I-Hui
IH
Yeh
Tzung-Lieh
TL
Yang
Yen-Kuang
YK
Ko
Huei-Chen
HC
Lu
Ru-Band
RB
D000328:Adult; D001288:Attention / Q000502:physiology; D001714:Bipolar Disorder / Q000145:classification* / Q000150:complications*; D003072:Cognition Disorders / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D009483:Neuropsychological Tests; D011340:Problem Solving / Q000502:physiology; D055815:Young Adult