Examination of time-dependent changes in neurocognitive functions in individuals with Bipolar disorder: A cohort study

Introduction: Bipolar disorder is a chronic illness, characterized by recurrent mood episodes. Neurocognitive dysfunction is frequent in bipolar disorder. Current research shows significant impairment in neurocognitive functions of bipolar disorder patients, compared to healthy controls.. The aim of this study is to determine whether neurocognitive functions of individuals with bipolar disorder change over time. Method: In this study, a 37-person group consisting of patients diagnosed with bipolar disorder whose neurocognitive tests were carried out at the Departments of Psychiatry and Neuroscience of Dokuz Eylül University 4-10 years ago were reevaluated in terms of their neurocognitive functions; and the data obtained were compared to the previous scores, as well as to the neurocognitive functions of 37 healthy participants who were participated to the studies conducted by our team. Results: Compared to the primary measurements, the patients shown significantly lower performance in terms of Digit Symbols (F = 0,471; t = -2,255; p < 0,027), Verbal Fluency (F = 1,172; t = 2,070; p = 0,042), Wisconsin Card Sorting Test (WCST) Category Number (Z = 370,500; p < 0,001), WCST Perseverative Error (Z = 806,000; p = 0,021), Visual Reproduction Delayed Recall (Z = 373,000; p = 0,43) and Category Fluency (Z = 460,000;p = 0,015) tests. Then, patients' primary scores were compared with the new scores obtained from the patients after 4-10 years. According to the analysis results, all subtest scores of Rey Auditory Verbal Learning Test (p <0.001; p <0.001; p <0.001, p = 0.010), Visual Reproduction Test Delayed Recall (p = 0.023), Auditory Consonants Trigram Test (p = 0.020) ), Digit Symbol Test (p = 0.038), Verbal Fluency Test (p = 0.038), Category Fluency Test (p = 0.006) and Stroop Test (p = 0.008) scores obtained from new neuropsychological test of bipolar patients were significantly lower compared to their previous scores. Conclusion: Patients diagnosed with bipolar disorder have shown impairment in short and long term memory, verbal memory, working memory, processing speed and attention in a 4-10-year period of time. On the other hand; there was no significant impairment in visual memory and executive functions such as mental flexibility, feedback utilization and problem solving. Key words: Neurocognitive functions, bipolar disorder, cohort, follow-up study