This book is a presentation of the results of the conclusion of the author's doctoral project entitled "Transcranial direct current stimulation (tDCS) and escitalopram in changing cognitive performance in patients with major depressive disorder in a randomized, parallel, double-blind, placebo-controlled clinical trial, presented to the Faculty of Medicine of the University of São Paulo to obtain the title of Doctor of Science. The text delves into current data on Major Depressive Disorder, the most commonly used forms of treatment and the promising results of neuromodulation, especially transcranial direct current stimulation (tDCS) as an adjunctive treatment for Major Depressive Disorder. In order to analyze this issue, data from the neuropsychological evaluation of patients from a randomized, double-blind, parallel and placebo-controlled clinical trial comparing tDCS and escitalopram in the treatment of patients with major depressive disorder were presented, seeking to verify differences between cognitive performance before and after each of the two techniques.