Major depressive disorder (MDD) is a common psychiatric condition, mostly treated with antidepressant drugs, which are limited for issues such as refractoriness and adverse effects. In this context, the investigators investigate a non-pharmacological treatment known as transcranial direct current stimulation (tDCS). To prove that tDCS is similarly effective than antidepressants would have a tremendous impact in clinical psychiatry, since tDCS is virtually absent of adverse effects. Its ease of use, portability and low price are also interesting characteristics for using in primary and secondary health care. Thus, our aim is to compare tDCS against a fully dosed, effective antidepressant. The study will be a non-inferiority, randomized, double-blinded, placebo-controlled, three-arm trial comparing active tDCS/placebo pill, sham tDCS/escitalopram 20mg/day and sham tDCS/placebo pill. Our primary aim is to show that tDCS is not inferior to escitalopram 20mg/day with a noninferiority margin of at least 50% of the escitalopram-placebo effect.

Major depressive disorder (MDD) is a common psychiatric condition, mostly treated with antidepressant drugs, which are limited for issues such as refractoriness and adverse effects. In this context, the researchers investigate a non-pharmacological treatment known as transcranial direct current stimulation (tDCS). In a prior clinical trial with 120 patients with MDD, the investigators demonstrated that the combination of tDCS with sertraline 50mg/day had increased, faster effects on depressive symptoms (Brunoni et al., JAMA Psychiatry, 2013). However, although the investigators suggested that tDCS vs. sertraline had similar efficacy, such comparison was compromised due to the low sertraline dose and also because the comparison of sertraline vs. placebo was not significant. To prove that tDCS is similarly effective than antidepressants would have a tremendous impact in clinical psychiatry, since tDCS is virtually absent of adverse effects. Its ease of use, portability and low price are also interesting characteristics for using in primary and secondary health care. Thus, our aim is to compare tDCS against a fully dosed, effective antidepressant. The study will be a non-inferiority, randomized, double-blinded, placebo-controlled, three-arm trial comparing active tDCS/placebo pill, sham tDCS/escitalopram 20mg/day and sham tDCS/placebo pill for ten weeks, randomizing 240 patients with MDD in a 3:3:2 ratio (less to placebo). Our primary aim is to show that tDCS is not inferior to escitalopram 20mg/day with a noninferiority margin of at least 50% of the escitalopram-placebo effect. As secondary aims, the researchers will investigate putative biomarkers for tDCS response. This is important considering the large sample size of this study and also the paucity of tDCS studies - therefore, the identification of such biomarkers could generate new hypothesis for future studies and for tDCS' mechanisms of action. The biomarkers will be: genetic polymorphisms (BDNF, SLC6A4, THP1, 5HT2A); serum markers (BDNF); motor cortical excitability (cortical silent period, intracortical inhibition, intracortical facilitation); heart rate variability; and neuroimaging (structural volume of the dorsolateral prefrontal and anterior cingulate cortex, white matter tracts of the prefrontal cortex and posterior cingulate cortex connectivity). This project represents a novel research line in our Institution, and the investigators thereby propose the onset of a new center denominated C.I.N.A. (Interdisciplinary Center for Applied Neuromodulation) that will foment the use and development of projects using neuromodulation techniques. This new center will also interact with other centers on the fields of clinical research, neurosciences and neuropsychiatry.

Inclusion Criteria:

• HAMD17>=17
• more than 8 years of schooling OR able to read, speak and understand the Portuguese language.
• Low suicide risk.

Exclusion Criteria:

• Bipolar disorders.
• Schizophrenia and other psychotic disorders.
• Anxiety disorders, if it is the primary diagnosis (comorbidity with depression is not an exclusion disorder)
• Substance abuse or dependence.
• Depression symptoms better explained by medical conditions.
• Neurologic conditions (e.g., stroke, multiple sclerosis, brain tumor).
• Severe medical conditions.
• Pregnancy/breast-feeding.
• Severe suicidal ideation, suicidal planning or recent (<4 weeks) suicide attempt.
• Contra-indications to escitalopram.
• Current use of escitalopram in the current depressive episode.
• Use of escitalopram in a prior depressive episode that was not effective.
• Contra-indications to tDCS.
• Previous use of tDCS (current or previous depressive episode).