Home tDCS for the Treatment of Major Depression.

Inclusion Criteria: * Spanish or Catalan speakers of both sexes between the ages of 18 and 65. * Patients diagnosed with major depression, based on the criteria in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Specifically, patients will be included who meet the criteria for a major depressive episode with a longitudinal diagnosis of major depressive disorder, single or recurrent episode; or bipolar disorder type 1 or 2. Patients must obtain a moderate or higher score, therefore we establish a lower limit of 15 points on the Montgomery-Åsberg Depression Rating Scale (MADRS) (Alonzo et al., 2019). * Patients receiving or not receiving pharmacological treatment for depression will be included, and this will be recorded as an additional variable. * Have the ability and willingness to commit to the study team for supervision of the intervention sessions and close monitoring of safety. * Demonstrate the acquisition of the ability to properly apply home tDCS independently or with the help of a companion. Exclusion Criteria: * Patients with psychotic, schizoaffective, or personality disorders (both cluster A and B). * Patients with a history of neurological disease, intellectual disability, or cognitive impairment (inability to understand instructions or operate equipment). * Any exclusion criteria established by clinical guidelines on non-invasive brain stimulation (Woods et al., 2016): metal implants or head injuries, any electronic devices such as cochlear implants or cardiac pacemakers. Brain stimulation in the last 6 months. Clinical or family history of epilepsy. * Patients with dermatological problems, such as an allergic skin reaction at the electrode site. * High risk of suicide. Assessed through an interview with a psychiatrist and the use of the Spanish-validated Columbia Suicide Risk Scale (C-SSRS) (Al-Halabí et al., 2016). * Drug or alcohol abuse during the study or in the previous 3 months (except for nicotine). * Changes in pharmacological or non-pharmacological treatment (such as structured psychotherapy) during the study or in the 3 months prior to starting the trial. * Pregnancy.