The aim is to investigate the effect of transcranial Direct Current Stimulation (tDCS) applied at the anodal left CDLPF of patients with resistant depression compared to patients treated with conventional therapy. The tDCS is used in add-on drug treatment in resistant depression stabilized for 4 weeks (antidepressant as SSRIs (Selective Serotonin Reuptake Inhibitors) or SNRIs (Serotonine-Norepinephrine Reuptake Inhibitors) for unipolar patients and lithium for bipolar patients). The delay of 4 weeks is a minimum to observe a non-response. Moreover, in term of ethical point of view, it's difficult to wait 6 to 8 weeks to observe the non-response to treatment.

This is a randomized 2-arm parallel, double blind study comparing 2 groups of 60 patients (48 unipolar plus 12 bipolar patients per group. Patients will be selected in the psychiatric department of the University Hospital of different centers and the two groups are matched for age (+/- 5 years), gender and depression diagnosis (unipolar vs bipolar).

After giving informed consent, patients will be evaluated by a psychiatrist using the Hamilton Depression Rating Scale (HDRS), Montgomery Asberg Depression Rating Scale (MADRS), the STAI and Beck Depression Inventory (BDI) and for bipolar patient only, by the Young Mania Rating Scale (YMRS). The complete assessment takes 50 minutes. A neuropsychologist assessment will be also realized during 20 minutes using the Crossing of Test (COT), the Trail Making Test (TMT), the Isaacs Set Test (IST) and the Cardebat fluency Task.

After locating the left DLPFC, treatment with active tDCS with a current of 2 mA or sham will be directed by 30-minute session. A psychometric assessment will be conducted again at the end of treatment week and 4, 12 and finally 24 weeks after stopping treatment. The neuropsychologist assessment will be conducted again 4 weeks after the end of treatment. Scales of comfort and acceptability will also be proposed to the patient to determine whether any gene is caused by this treatment.

These people will be recruited on a voluntary basis, after notification and consent in the 6 research centers. This study was conducted over a period of 36 months.

This study was supporting by a grant from the French Hospital Program of Clinical Reseach (PHRC N/2011-60-2011-A01074-37)

Inclusion Criteria:

• subject whose MDD are single or recurrent without psychotic features according to DSM-IV-TR
• subject with a diagnosis of resistant major depression (≥1 failed antidepressant treatments for the current depressive episode)
• HDRS-21 score ≥ 21
• drug treatment by SSRIs or SNRIs for unipolar patients or with Lithium for bipolar patients for at least 4 weeks
• right-handed patients
• without severe progressive somatic pathology (especially tumor diseases, degenerative diseases)
• without severe cognitive impairment making psychometric evaluation impossible
• excepted antidepressant or Lithium treatment, psychotropic following are tolerated during the course of the study : hydroxyzin; cyamemazin (up to 100 mg/day) ; hypnotics (imidazopyridin).

Exclusion Criteria:

• subject treated with antipsychotics or mood stabilizers or anticonvulsants or by ECT or rTMS for the current depressive episode
• subject resistant to SSRIs or SNRIs for unipolar patients or with Lithium for bipolar patients
• subject with mixed features
• pregnancy and/or lactation
• presence of a specific contraindication for tDCS (e.g., personal history of epilepsy, metallic head implant, cardiac pacemaker)