Cognitive Dysfunction and Improvement after Antidepressant Treatment in Patients with Non-Psychotic Major Depressive Disorder in Mild to Moderate Severity: A Prospective Study

Lee, Kang Uk; Cho, Seong Myung; Park, Jong Ik

Abstract

OBJECTIVE
This study was conducted to evaluate the impairment of cognitive functions, which include verbal and visual memory, visuospatial function, and executive function, and also to investigate if there is improvement of cognitive impairment after antidepressant treatment in patients with major depressive disorder (MDD).
METHODS
Fifteen female patients with non-psychotic MDD in mild to moderate severity and 25 age-matched female normal control subjects participated in this study. Clinical severity of depression was measured by Beck Depression Inventory (BDI), Zung's Self-Rating Depression Scale (Zung), and Hamilton Rating Scale for Depression (HAMD). Cognitive functions were tested using Ray Complex Figure Test (RCFT) to evaluate visuospatial function and visual memory, Stroop test to evaluate conflict monitoring, Wisconsin Card Sorting Test (WCST) to evaluate executive function, and Seoul Verbal Learning Test (SVLT) to evaluate verbal memory. Both clinical depression scales and cognitive function tests were conducted at baseline and after 12 months of antidepressant treatment.
RESULTS
At baseline, there were deficits in immediate and delayed recall of SVLT in patients with MDD compared to normal control subjects, while the impairment in visuospatial function, visual memory, and executive function was not clear. After antidepressant treatment, improvement of executive function, i.e. percent of error response and perseverative response of WCST in MDD patients was greater than that in normal control subjects. Improvement of executive function, however, did not show a significant correlation with the change of clinical severity of depression.
CONCLUSION
The verbal memory was the most prominent domain of cognitive dysfunction in non-psychotic depression with mild to moderate severity. Of further note, differential improvement in executive function was observed in MDD patients after antidepressant treatment, although the improvement in executive function was not directly associated with the improvement of clinical depression.