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.