Neuropsychological functions in patients with bipolar I and bipolar II disorder.

UNLABELLED: 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.

Neuropsychological functions in Han Chinese patients in Taiwan with bipolar II disorder comorbid and not comorbid with alcohol abuse/alcohol dependence disorder.

OBJECTIVE: Studies exploring neuropsychological functions of bipolar disorder (BP) specifically include patients comorbid with alcohol abuse (AB), alcohol dependence (AD), or both (AB/AD). Contradictory assessments of neuropsychological impairment may be caused by not excluding the confounding effects of comorbid AB/AD. Most of the literature discusses BP without subtyping, which overlooks that BP-II may be a valid diagnosis different from BP-I. Because neuropsychological functions are involved in overall BP-II outcomes, we hypothesized that the neuropsychological functions of patients with BP-II comorbid with AD (BP(+AD)) are significantly different from and more impaired than those of patients with BP-II not comorbid with AD (BP(-AD)). METHODS: Using DSM-IV criteria, the study included 69 patients with BP-II (19 with BP(+AD); 28 with BP(-AD)) and 22 healthy controls compared using a battery of neuropsychological tests that assessed memory, psychomotor speed, and certain aspects of frontal executive function. All BP-II patients were in an inter-episode period (a period of remission between states of mania, hypomania, and depression). RESULTS: BP(+AD) patients had lower scores than did BP(-AD) patients and controls in verbal memory, visual memory, attention, psychomotor speed, and executive function. Working memory was poorer for BP(+AD) than BP(-AD) patients and for both BP groups than for controls. CONCLUSIONS: BP(+AD) patients manifested wide neuropsychological dysfunctions, and BP(-AD) patients showed a reduction in working memory, which suggested that working memory might be related to a history of BP-II. Neuropsychological dysfunctions seemed more strongly associated with AB/AD than with BP-II in inter-episode periods.