Several studies have shown that tDCS is valuable and safe options to improve depressive symptoms in adult patients . However, regarding the tDCS to treat depression in elderly population, only few studies have been reported, and there is no consensus among them. To our knowledge, prefrontal cortex tDCS could be reasonably safe and efficient options for the treatment of several psychiatric illnesses in a population presenting resistance to and/or intolerance of pharmacotherapy . Moreover, the safety tolerability profile of tDCS is a strong argument in favour of exploring their use in the depressed population. Therefore, current study will investigate the efficacy and safety of prefrontal tDCS used as additive treatment in patients with LLD.

Inclusion Criteria:

1. Participants who meet the criteria of major depression defined by DSM-5 criteria
2. Participants will be non-responders and taking an antidepressant of adequate dose and for ≥4 weeks in the current episode which has not led to sufficient clinical improvement (defined as a minimum level of 2 on the ATHF); or can't tolerate the adverse effects of antidepressant in the current episode
3. Ambulatory participants with or without any aiding device

Exclusion Criteria:

1. An urgent risk of suicide or severe depression
2. A history of ineffectiveness with tDCS
3. People who are clinically contraindicated to receive tDCS intervention or MRI assessment, such as having any brain lesion, intracranial implants (clips, cochlear implants), a tattoo or metal embedded in their scalp or brain
4. Any instable medical condition
5. A history of epilepsy,
6. A history of substance use (within one year)
7. People with dementia or psychotic disorder.
8. Any condition which would make the subject unsuitable for the study under the physician's assessment.