Transcranial Direct Current Stimulation (tDCS) as an Adjunctive Treatment for Treatment Resistant Depression (TRD)

Inclusion Criteria * 18 years and older * Clinical diagnosis of treatment-resistant depression (defined as depression that does not remit following two or more treatment attempts of an adequate dose and duration of a minimum duration of 4 weeks) * Hospitalized in psychiatric units * Voluntary admission status * Moderate or severe depression, defined by PHQ-9 ≥ 15 * Ability to provide informed consent * Ability to adhere to protocol Exclusion Criteria * Bipolar disorder * Active primary psychotic or substance use disorders (except nicotine dependence) within the past year * Any active neurological condition (including seizure disorder, traumatic brain injury, stroke) * Contraindications to tDCS (including pacemaker, metallic implants in the head or neck \[except orthodontic hardware\], skin disease causing irritation) * Current pregnancy or positive urine pregnancy test (clinical) * Any neuromodulation therapy (including ECT, rTMS, DBS, VNS, TES) within the last 3 months