Investigating cognitive functions in euthymic bipolar patients on mono versus polypharmacy in comparison to healthy controls

Objective: Bipolar disorder is a chronic mental disorder with cognitive impairment. Although conflicting, data pointo to possible deteriorating effect of psychotrops on cognitive functions. The aim of this study was to investigate cognitive functions in euthymic bipolar patients who are on mono versus polypharmacy in comparison to healthy controls. We hypothesized that polypharmacy would have a more negative impact on neurocognitive functioning than monotherapy.Method: Forty eight euthymic patients with DSM-IV bipolar disorder either on mono (n=21) or polypharmacy (n=27) and 40 sex and age matched healthy controls were enrolled in the study. Patiens were evaluated with psychiatric interview, Young Mania Scale and Hamilton Depression Scale. A large neurocognitive battery was used for neurocognitive assessment. Kruskal Wallis, Mann Whitney-U, chi-square, Spearman and Pearson correlation and multiple regression tests were used for statistical analysis.Results: Both patient groups performed significantly worse than healthy controls in almost all cognitive areas. Patients on single medication did significantly worse than patients on combination treatment. . Neurocognitive performance was positively correlated with the lenght of education in the whole group but negatively correlated with duration of illness in the patient group. After controlling for education years and duration of illness, multiple regression analysis in the patient group revealed a significant difference on the digit span test-backward scores where patients on monotherapy did worse than the patients on polypharmacy.Conclusion: Results point to a possible medication effect on working memory. In contrast to our hypothesis, combination treatment would be more preferrable than monotherapy for a better working memory function in bipolar disorder.Key words: bipolar disorder, euthymia, cognitive functions.