This study will investigate whether transcranial direct current stimulation (tDCS) can enhance the efficacy of cognitive behavioural therapy for the treatment of depression.

Inclusion Criteria:

1. Participants will be ≥ 18 years old.
2. Have a DSM-IV diagnosis of Major Depressive Episode of minimum 4 weeks duration.
3. MADRS score ≥ 20 at study entry.

Exclusion Criteria:

1. Participant is unable to give informed consent.
2. DSM-IV diagnosis of psychotic disorder (lifetime).
3. Bipolar disorder diagnosis and not on a mood stabiliser.
4. Eating disorder (current or within past year).
5. Obsessive compulsive disorder (lifetime).
6. Post-traumatic stress disorder (current or within past year).
7. Mental retardation.
8. Drug or alcohol abuse or dependence (preceding 3 months).
9. Inadequate response to ECT (current episode of depression).
10. Rapid clinical response required, e.g., high suicide risk, inanition or psychosis.
11. Clinically defined neurological disorder or insult.
12. Metal in the cranium, skull defects, or skin lesions on scalp (cuts, abrasions, rash) at proposed electrode sites.
13. Pregnancy.
14. Concurrent long acting benzodiazepines, ritalin or dexamphetamine medication.
15. Change in psychotropic medication during 2-week period prior to the study or during the course of the 3-week trial.
16. Participant becomes hypomanic or manic, as defined by DSM-IV.