Factors associated with the discrepancy between objective and subjective cognitive impairment in bipolar disorder

The aim of this study is to evaluate the discrepancy between objective cognitive measures and cognitive subjective complaints in a sample of euthymic patients with bipolar disorder (BD).

One hundred and sixteen participants (83 euthymic patients with BD and 33 healthy controls) were enrolled for this study. Patients were assessed with a comprehensive neuropsychological battery and they also reported their subjective cognitive complaints with the Cognitive Complaints in Bipolar Disorder Rating Scale (COBRA). The discrepancy between objective and subjective data was calculated using a novel methodology proposed in a previous study (Miskowiak, 2016). Statistical analyses included Pearson correlations and multiple linear regression.

Higher number of previous depressive episodes was identified as one variable associated with the global sensitivity composite score (Beta = 0.25; t = 2.1; p = 0.04) and with the verbal learning and memory sensitivity score (Beta = 0.26; t = 2.16; p = 0.03). That is, patients with more previous depressive episodes tend to over-report cognitive complaints. In contrast, higher number of previous hospitalizations was associated with stoicism in the global total score (Beta = -0.27; t = -2.24: p = 0.029) and in the domain of attention/processing speed (Beta = -0.34; t = -2.52; p = 0.016), indicating patients with more hospitalizations tend to report less cognitive complaints.

Our study identified some factors that might help to explain the discrepancy between objective and subjective cognitive measures in BD, including number of previous depressive episodes and number of previous hospitalizations. This highlights the need of the combined use of both types of cognitive measures to make an accurate assessment of cognitive dysfunctions and their effective treatment.