tDCS for Late-Life Depression

Inclusion Criteria: Participants must meet all of the following criteria: 1. age 60 years or older; 2. diagnosis of unipolar major depressive disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), confirmed by the Structured Clinical Interview for DSM-5 (SCID-5); 3. score of 16 or higher on the Quick Inventory of Depressive Symptomology-Clinician Rated (QIDS-C) at screening; 4. stable antidepressant regimen for at least four weeks prior to enrollment, if applicable; 5. willingness and capacity to provide informed consent; 6. Clinical Dementia Rating scale of 0 or 0.5. 7. availability of an informant who has sufficient knowledge of the participant's daily functioning as ascertained by the study team. Exclusion Criteria: Participants meeting any of the following criteria will be excluded: 1. contraindications to tDCS including metallic cranial implants, skin conditions at electrode sites (eczema, open wounds, burns, lesions), or history of adverse reaction to tDCS; 2. contraindications to magnetic resonance imaging (MRI) including pacemaker, cochlear implants, ferromagnetic implants, or claustrophobia; 3. depressive disorder due to a medical condition; 4. psychotic depression; 5. history of seizures or epilepsy; 6. bipolar disorder; 7. psychotic disorders; 8. severe personality disorder; 9. active substance use disorder within the past six months or history of substance induced mood or psychotic disorder; 10. neuromodulation treatment including electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), tDCS, or vagus nerve stimulation (VNS) within the past six months; 11. active suicidal ideation with plan or intent requiring a higher level of care; 12. concurrent use of medications that substantially lower seizure threshold; 13. pregnancy; 14. a clinically established diagnosis of dementia as reported in the participant's health record or scoring 1 or above on CDR; 15. medically unstable in the clinical opinion of the principal investigators.