Abstract
Cognition dysfunction may reflect trait characteristics of bipolarity but cognitive effects of medications have confounded previous comparisons of cognitive function between bipolar II and unipolar depression, which are distinct clinical disorders with some overlaps. Therefore, we examined the executive function (WCST), attention, cognitive speed (TMT-A) and memory (CAVLT, WMS-Visual reproduction) of 20 treatment-naïve bipolar II patients (BPII), 35 treatment-naïve unipolar depressed (UD) patients, and 35 age/sex/education matched healthy controls. The subjects were young (aged 18–35), and had no history of psychosis or substance use, currently depressed and meeting either RDC criteria for Bipolar II Disorder or DSM-IV-TR criteria for Major Depressive Disorder. The patients were moderately depressed (MADRS) and anxious(HAM-A), on average within 3.44 years of illness onset. Sociodemographic data and IQ were similar between the groups. UD patients had significantly slower cognitive speed and cognitive flexibility (WCST perseverative error). BPII depressed patients showed relatively intact cognitive function. Verbal memory (CAVLT List A total) correlated with illness chronicity only in BPII depression, but not UD. In conclusion, young and treatment-naïve BPII depressed patients differed from unipolar depression by a relatively intact cognitive profile and a chronicity-cognitive correlation that suggested a stronger resemblance to Bipolar I Disorder than Unipolar Depression.
Highlights
Another way to elucidate the role of cognitive impairment in bipolar disorders is to examine such impairment in bipolar II (BPII) depression vs unipolar depression (UD)
The bipolar II patients (BPII), unipolar depressed (UD) and healthy controls (HC) groups were comparable in age, gender and other socio-demographic variables including occupational status, marital status and family income. (Table 1)
UD and BPII subjects were comparable in the significantly reduced SF-36 physical and mental component summary scores compared to healthy controls, reflecting impaired health-related quality of life (Table 2)
Summary
Another way to elucidate the role of cognitive impairment in bipolar disorders is to examine such impairment in bipolar II (BPII) depression vs unipolar depression (UD). The different types of medications (antidepressants versus mood stabilisers) received by unipolar and bipolar patients may have different sustained impact on the cognitive function studied. We set out to examine the cognitive function of young and treatment-naïve bipolar II and unipolar depressive patients with no history of psychosis or substance use, versus age/sex-matched controls to better elucidate trait-related variation in cognitive function in bipolar II disorder. They were compared with age/ sex-matched healthy controls. To examine the nature and differences of cognitive impairment in drug-naïve and young BPII depressed and unipolar depressed patients. To explore in BPII depressed and unipolar depressed patients the correlation between cognitive impairment with illness chronicity and current affective symptoms
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