Assessment of executive functions in bipolar depression

Abstract

Introduction Cognitive functions in bipolar disorder have been assessed during acute mood episodes but also during remission. While other cognitive functions, such as verbal and working memory, attention, verbal fluency and psychomotor speed seem to recover after the acute episode, executive functions impairment remains also during remission; this aspect led to the assumption that executive functions may be a trait marker for bipolar disorder. Objective The purpose of this study was to assess the executive functions, such as cognitive flexibility, set shifting, problem solving and abstract thinking in bipolar depression compared to healthy subjects. Method Forty patients diagnosed with Bipolar Disorder and Major Depressive Episode according to DSM IV-TR were included into the study. Executive functions were investigated using Wisconsin Card Sorting Test (WCST). Results obtained by patients were compared with those of 30 healthy who underwent the same cognitive evaluation. Results Depressed bipolar patients scored significantly worse on the majority of WCST measures. Thus, for total trials, total errors, preservative errors and preservative responses (raw scores and percents) and failure to maintain set scores, the differences between the two groups were significant at the 1% threshold ( P =0.000). The patients and controls displayed similar behavior for total correct ( P =0.215) and conceptual levels scores ( P =0.421). Conclusions Patients with bipolar disorder show during a depressive episode difficulties in most cognitive tasks involving executive functions. Results obtained by patients at failure to maintain set score suggest frontal dysfunctions for this category of patients.