## 4 Conclusions  
This current review explores tDCS and tMS as effective alternatives or adjuncts to traditional therapies for MDD as a possible solution for those who are resistant to conventional treatments or cannot tolerate the side effects of sequestration. tDCS is a noninvasive, inexpensive method with no significant or short-term side effects.  
tDCS treatment shows greater clinical efficacy, as measured by response rate, remission, and ongoing symptom assessment, compared with a placebo tDCS intervention. Recent studies have shown that tDCS improved depressive symptomatology and cognitive functions associated with depression, such as memory and attention.  
However, despite significant advances in understanding its effects, tDCS is still not completely understood, particularly regarding its mechanisms and long-term efficacy. The lack of inferiority to antidepressant treatment has not yet been demonstrated. The mechanism proposed is neuroplasticity, with effects observed at the neuronal level. Evidence for neuroplastic effects mediating clinical outcomes in MDD is limited. Identifying predictive biomarkers is essential for understanding the pathophysiology of the disease and would help guide clinical decisions.  
In the case of tMS, the efficacy is improved by lateralizing LF-TMS and HF-rTMS following the functional brain asymmetry that has been highlighted in the literature in the case of depression. However, not all patients have the same brain activity underlying depression. Individualizing tMS protocol parameters such as frequency and stimulated area may increase the antidepressant effect [91].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Therapeutic Approach** & **Type of Depression 1** & **Outcome** & **References** \\ \hline tMS + Excitalopram & & Depressive symptoms \(\succ\) & [87] \\
15 Hz: 15 sessions—20 mg & MRMD & HAM-D above 0.70 & [88] \\ \hline rTMS + verlalexite/serstalopram & & & Depressive symptoms \(\succ\) & \\  & & & no difference between drugs & \\  & & & & \\  & & & & \\  &  
Future directions in studying tDCS should be focused on exploring the neurobiological mechanisms by which tDCS affects cognitive and emotional processes. This may help to identify the specific neural changes and pathways that are involved. Moreover, investigating the effects of tDCS combined with pharmacotherapy, psychotherapy, and cognitive rehabilitation could help to improve functional and cognitive outcomes in treatment-resistant patients. More studies in diverse demographic and clinical populations are essential, including studies in rural and low-resource settings where tDCS could be a valuable alternative because of its portability and affordability. These future directions could position tDCS as a more integrated component of treatment protocols for MDD, possibly offering patients a pathway to enhanced cognitive and emotional well-being.  
Conceptualization, F.Z. and B.M.R.; methodology, F.Z, D.-M.T. and C.D.; writing--original draft preparation, F.Z., D.-M.T., A.B. and C.D., writing--review and editing, B.M.R.; supervision, B.M.R. All authors have read and agreed to the published version of the manuscript.  
No funding was received for conducting this study.  
Not applicable.  
No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
The authors declare no conflict of interest.