The impact of high-frequency repetitive transcranial magnetic stimulation on executive functioning of drug-free patients with treatment-resistant depression

OBJECTIVES: The aim of the present study was to examine the impact of 25 Hz high-frequency repetitive transcranial magnetic stimulation (rTMS) on neuropsychological testing in treatment-resistant depression patients who were receiving no other concomitant medications for the treatment. METHODS: A total of 19 patients with treatment-resistant depression and 20 healthy controls were included in the study. A 25 Hz, 1000 pulse stimulation was set at 100% of the motor threshold and delivered 20 times for 2 s with 30 s intervals as 20 sessions to the depression group, and sham treatment was applied to the control group. Brief Psychiatric Rating Scale (BPRS), Stroop task, trail-making test (TMT), and Wisconsin card sorting test (WCST) were performed both before and 3 days after the rTMS treatment. Seventeen-item Hamilton Depression Rating Scale (HAMD) and Beck Depression Inventory (BDI) were obtained at baseline and after the rTMS treatment, as well. RESULTS: After the rTMS treatment, 52.6% (10 of 19 patients) met the response criteria (>50% improvement in HAMD score), with 5 (26.3%) patients meeting the criteria for remission of depression (HAMD score <= 8). None of the patients had a worsened HAMD score at the end of treatment. Reflecting the antidepressant effect of rTMS treatment, the mean BDI score, BPRS score, and Stroop task scores significantly differed following the treatment (p < .001, p < .001, and p = .017, respectively). TMT score difference did not reach statistical significance, whereas WCST scores showed significance in "correct responses" and "perseverative errors" categories (p < .05, and p < .05, respectively). None of the test scores at the end of rTMS treatment showed a significant difference when compared to baseline scores for the control group (p > .05, for all). CONCLUSIONS: Results suggest that rTMS can be used as a beneficial treatment option to ameliorate cognitive functions, especially executive functions. Patients had an improvement in depressive symptoms with the rTMS treatment without any concomitant medication, as well. Therefore, improvement in cognitive performance might be associated with improvement in depressive symptoms.