Assessment of cognitive functions in euthymic patients with bipolar II disorder compared with healthy controls

Background: There is increasing evidence that several cognitive areas are impaired during the acute phases of bipolar disorder (BD) and that this impairment persists even in the euthymic periods. The BD-II population has not been assessed in this aspect, mainly because of the small number of patients with BD-II.

Aim: The aim of this study was to compare the cognitive performance of patients with BD-II with a healthy control group by demonstrating the range of neuropsychological deficits in the various cognitive domains in euthymic BD-II patients.

Participants and methods: The study included 30 euthymic patients with BD-II [diagnosed using Structured Clinical Interview for DSM-IV (SCID-I) and the euthymic state determined using the Young Mania Rating Scale and the Hamilton Rating Scale for Depression], who were compared on neuropsychological variables (e.g. executive function, attention, and verbal and visual memory) and contrasted with 30 healthy controls without a history of neurological or psychiatric disorders on cognitive performance.

Results: Compared with the controls, BD-II patients showed significant deficits in most cognitive tasks including the majority of domains of the Wechsler Adult Intelligence Scale, verbal intelligence quotient (P = 0.003) and comprehension (P=0.004), and on digit symbol (P = 0.049), memory functions (Wechsler Memory Scale; P=0.000), sustained attention (Continuous Performance Test; P=0.031), and executive functions [maintain set (P=0.008), learn category (P = 0.007), and categories completed (P = 0.012)].

Conclusion: We conclude that cognitive impairment exists during the period of euthymia in BD-II. These cognitive difficulties, especially related to verbal memory, may help in explaining the impairment in daily functioning and may aid the formulation of a special rehabilitation program for them.