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Objective: The aim of this study was to compare patients with bipolar disorder type I (BD) with and without comorbid borderline personality disorder (BPD), in euthymic period, in terms of cognitive functions. The main hypotesis of this study was that cognitive functions would be more impaired in patients with BD with comorbid BPD (BD + BPD).
Methods: The structured clinical interviews for diagnostic and statistical manual of mental disorders-IV axis I disorders (SCID-I and SCID-II) were administered to 105 patients and the patients were separated into two groups as 79 BD patients and 26 BD plus BPD patients. Young Mania Rating Scale, Hamilton Depression Rating Scale, California verbal learning test, Wisconsin card sorting test, trail-making test (TMT), and stroop test were administered to the both groups.
Results: BD with comorbid BPD group showed statistically significantly lower performance in the average scores of TMT-A seconds and errors, and TMT-B seconds scores than the BD group (respectively t = −3.449, p = .001; t = −3.431, p = .001; t = −2.331, p = .022).
Conclusions: The processing speed, set shifting, and selective attention in BD with comorbid BPD group is more disturbed than the BD group. We suggest that when evaluating the cognitive functions, evaluation of comorbid psychiatric diagnosis, especially BPD, is crucial in BD