RESUMEN
BACKGROUND: The efficacy of transcranial direct current stimulation (tDCS) as a continuation therapy for the maintenance phase of the depressive episode is low and insufficiently investigated in literature. We investigated whether it could be enhanced by using a more intensive treatment regimen compared to previous reports. METHODS: Twenty-four patients (16 with unipolar depression and eight with bipolar depression) who presented acute tDCS response (≥50% depression improvement in the Hamilton Depression Rating Scale [HDRS]) after receiving 15 tDCS sessions were followed for up to 6 months or until relapse, defined as clinical worsening and/or HDRS > 15. Sessions were performed twice a week (maximum of 48 sessions) over 24 weeks. The anode and the cathode were positioned over the left and right dorsolateral prefrontal cortex (2 mA current, 30 min sessions were delivered). We performed Kaplan-Meier survival analysis and Cox proportional hazards ratios to evaluate predictors of relapse. RESULTS: Out of 24 patients, 18 completed the follow-up period. tDCS treatment was well tolerated. The mean survival duration was 17.5 weeks (122 days). The survival rate at the end of follow-up was 73.5% (95% confidence interval, 50-87). A trend (P = 0.09) was observed for lower relapse rates in nontreatment- vs. antidepressant treatment-resistant patients (7.7% vs. 45.5%, respectively). No differences in efficacy between unipolar and bipolar depression were observed. CONCLUSION: An intensive tDCS treatment regimen consisting of sessions twice a week achieved relatively low relapse rates after a 6-month follow up of tDCS responders, particularly for nontreatment-resistant patients.