The purpose of this study is to assess safety and efficacy of nodal transcranial direct current stimulation in pediatric and teenager population with major depressive disorder in the COVID-19 pandemic.

After being widely informed about the study and potential risks, all the patients giving voluntary informed consent will be randomized in a 1:1 ratio to a tDCS group (a-tDCS+ standard treatment) or control group (placebo-simulations a-tDCS+ standard treatment).

Inclusion Criteria:

• Major Depressive Disorder (MDD) diagnosed through the clinical interview based on the Affective Disorders and Schizophrenia Agenda for schoolchildren-current version and for life K- SADS-PL for its acronym in English, with a single or recurrent episode lasting ≥4 weeks.
• The current depressive episode must have a duration of less than 5 years and be at least greater than 2 months in which the patient meets the operational definition of MDD from the DSM-V.
• CID scale with values equal to 17 or higher in the clinical evaluation.
• No use of another medication during the intervention days.
• They should not be taking antidepressants at the beginning of the study (last 4 weeks) or it must have passed the adequate time of "washing"/ clearance of antidepressant drugs established as 5 or more biological half-lifes or 5 days before the randomization.
• To be able and willing to give their informed consent, both, the parent or tutor and the participant who is between the ages of 14-17 years. In the age group of 10-13 years the assent of the patient and the consent of the parent or tutor.
• Use of benzodiazepines (eg lorazepam) equivalent to 20 mg of diazepam and which remains stable during the study.
• Patients with an unchanged drug treatment for MDD in the last 4 weeks and who agree to switch the fluoxetine at the time of randomization, meeting the previously described antidepressant criteria.

Exclusion Criteria:

• Previous skull surgery.
• Recent skull injury (6 months).
• Use of central nervous system stimulants.
• Respiratory System infections.
• Does NOT sign or is unable to sign informed consent or legal tutors/parents do not consent.
• Clinical condition or anomaly, which in the researcher's opinion, compromises patient´s safety or data quality.
• Uncontrolled co-existent medical condition, progressive cerebral disorder, severe systemic diseases, symptomatic disease, cardiac disease, skin chronic diseases or damaged scalp which could interfere with tDCS stimulation.
• Any skull metal implant (excluding dental filling or titanium plates) or medical devices (cardiac pacemaker, deep cerebral stimulator, drug infusion pump, cochlear implant, vagus nerve stimulator).
• Direct researcher relatives or personnel directly involved in the study.
• Acute suicide risk measured through the Montgomery Asberg depression rating scale (MADRS) >4 points or positivity of the 4th or 5th item of The Columbia Suicide Severity Rating Scale (C-SSRS).
• Depression resistant to treatment with >4 well indicated drugs during the current episode.
• Bipolar disorder history or current mania symptoms.
• Treatment with electroshock therapy concomitantly and during the last 12 months.
• Other relevant psychiatric disorders according to the DSM 5 (except generalized anxiety disorder, specific phobia or separation anxiety disorder).
• Previous treatment with tDCS for a different disease to the major depressive disorder.
• Intellectual development disorder previously documented or clinical evaluation fulfilling the CIE-F79 criteria.
• Due to the fact that treatment with tDCS has counter-indications, will be excluded: those with history of non provoked seizures, convulsive disorders, history of febrile seizure, family history of epilepsy or brain tumor, pregnancy.
• Counter-indication or history of adverse reactions from mild to severe to fluoxetine.

Elimination criteria:

• Patients that do not complete the neuropsychological assessment tests.
• Interruption of the intervention of less than 50% of what was scheduled.
• Onset of active suicidal ideation.
• Active psychosis.
• Start of emerging mania treatment.
• Pregnancy.

Personal data information will remain with strictly confidential character in the research center. However, personal data will be examined by all individuals related to the research project and/or those selected for its analysis, including representatives of Mexican health authorities and other regulatory agencies with inspection purposes.

If the data obtained through this study is published, the report will be written in a way no person could identify their personal data or identity, unless such information is officially required by any mexican or foreign authority.

In addition some of the personnel (evaluators, data analyst, result analyst) will be blinded in order to increase the internal validity of our study. A blind person is considered by the person that apply the intervention.