4. Discussion
TMS on cognitive functions, treatment-resistant depression, treatment-resistant MDD, cognitive impairment, Cognitive deficits, depressive disorder, depressive, MDD, depression, cognitive defects
CORTEX
The main outcomes of the current study were that TMS is an effective treatment in treatment-resistant depression, and can provide improvements in cognitive functions. Taking into account the importance of cognitive impairment in predicting the prognosis, life quality, functioning and risk of relapse in depression, the results of this study showed some novel promise.In this study, in which the efficacy of TMS treatment in treatment-resistant MDD was evaluated, a significant decrease was determined in the MADRS and HAM-D points in both groups after the procedure compared to preprocedure. These results show that TMS also has a significant placebo efficacy. Nevertheless that a greater improvement was seen in the treatment group than in the sham group was similar to the findings of previous metaanalyses that have shown the superiority of TMS treatment to sham TMS [In the majority of studies of TMS treatment that have included patient groups with depression, the mean HAM-D points have been reported to be 19 to 30 [It is known that there are impairments in attention, memory and executive functions in patients with depression [The dorsolateral prefrontal cortex (DLPFC) has been shown to be the area responsible for the executive functions of the prefrontal cortex, which are thought to have a significant role in the etiology of MDD [The Victoria Stroop test form, which evaluates selective attention, focussed attention, response inhibition, resistance to interference, and information processing speed, was used in this study. According to the mean points of all 3 sections of the test, the patient group showed a worse performance than the control group, but posttreatment, there was observed to be a significant improvement in the group that received the active TMS. These results suggest that in patients with depression, complex attention, mental flexibility, and the skills to be able to resist interference and inhibit response are impaired, and TMS treatment could have positive effects on these abilities. Stroop test is a reliable measurement of top to bottom attention control, including long-term attention and inhibition, and the increase in general performance in the Stroop test that was seen in the current study with the application of rTMS to the DLPFC was consistent with the literature [DST is a test which measures the ability to perceive and repeat audio stimuli, and allows interpretation of short-term memory, attention, and working memory. The significantly higher mean DST points of the control group than the patients in the current study showed that instant short-term memory and attention were impaired in the patients with depression. Although there was a decrease in the severity of depression following active TMS treatment compared to the sham group, no significant change was observed in the DST, which suggested that while there was earlier improvement in the numerical areas of cognitive functions, the improvement in audio attention and memory-related functions may occur later.That an improvement was determined in the sham group compared to the active TMS group in the VMPT was evaluated as a contradictory finding. In addition to showing no significant improving effect on verbal learning and memory processes, these results raise the question of whether TMS could suppress audio attention and memory in the early period. To be able to answer this question, there is a need for further more detailed observational studies of larger samples to investigate the effect of TMS on cognitive functions.Trail Making test (TMT) is a test which measures executive functions such as complex attention, set changing, and planning, which require visual-mechanical processing skills. The TMT-A evaluates processing speed related to visual scanning ability, and the TMT-B evaluates the ability to switch the setup and follow the sequencing [The effects of TMS on depressive disorder were evaluated in this study with the MADRS and HAM-D scales, and the data showed that TMS was effective on depressive symptoms. However, previous studies that have used the sham TMS protocol at an angle of 45° to minimise the actual stimulus effects have stated that there could be a partial active stimulus which could provide the targeted clinical improvement, indicating that the results could be debatable [Cognitive deficits in MDD make a significant contribution to the disabling effects on daily functioning and work performance [It has also been reported in the literature that cognitive symptoms may be seen before the onset of MDD [It has been reported that TMS does not have a negative effect on cognitive functions and it is also stated in the literature that TMS has improving effects on cognitive functions [There were some limitations to this study, primarily that because of the effect of the COVID-19 pandemic there were interruptions to the data collection process, some patients left the study before completion and new patients could not be included because of the halting of outpatient TMS protocols. The low number of study participants created a limitation in the comparisons made. Another limitation of the study was the statistically higher education level and employment status of the control group than the patient group. In addition, the effect of TMS alone could not be evaluated as the patients continued pharmacological treatments throughout the study. That a neuronavigation method for localization of the area to which TMS was to be applied and a sham headpiece could not be used because of the high cost entailed also constituted limitations of the study.In conclusion, the results of the current study demonstrated that with the exception of verbal memory processes, there was a tendency for improvement in the cognitive defects determined in the active phase of resistant depression following TMS treatment, and therefore the clinical use of TMS could provide improvement in cognitive functions in the early stage. However, as lover performance was shown on verbal learning and memory processes in the active stimulation group, these results raise the question of whether TMS could suppress audio attention and memory in the early period.
The authors declared have no conflicts of interest with respect to their authorship or the publication of this article.
The authors reported there is no funding associated with the work featured in this article.