Transcranial direct-current stimulation (tDCS) for bipolar depression: A systematic review and meta-analysis

- tDCS significantly improves symptoms of bipolar depression.
- tDCS can potentially cause a manic switch in patients with bipolar depression.
- RCT comparing tDCS antidepressant effect vs placebo are required to explore the effectiveness of tDCS in bipolar depression.

ObjectiveBipolar disorder (BD) is a severe and recurrent brain disorder that can manifest in manic or depressive episodes. Transcranial Direct Current Stimulation (tDCS) has been proposed as a novel therapeutic modality for patients experiencing bipolar depression, for which standard treatments are often inefficient. While several studies have been conducted in this patient group, there has been no systematic review or meta-analysis that specifically examines bipolar depression. We aimed to address this gap in the literature and evaluated the efficacy and tolerability of tDCS in patients fulfilling DSM-IV-TR criteria for BD I, II, or BD not otherwise specified (NOS).MethodsWe systematically searched the literature from April 2002 to November 2016 to identify relevant publications for inclusion in our systematic review and meta-analysis. Effect sizes for depression rating-scale scores were expressed as the standardized mean difference (SMD) before and after tDCS.ResultsThirteen of 382 identified studies met eligibility criteria for our systematic review. The meta-analysis included 46 patients from 7 studies with depression rating-scale scores pre- and post-tDCS. Parameters of tDCS procedures were heterogeneous. Depression scores decreased significantly with a medium effect size after acute-phase of treatment (SMD 0.71 [0.25-1.18], z = 3.00, p = 0.003) and at the furthest endpoint (SMD 1.27 [0.57-1.97], z = 3.57, p = 0.0004). Six cases of affective switching under tDCS treatment protocols were observed.ConclusionsDepressive symptoms respond to tDCS in patients with BD. Additional studies, and particularly randomized controlled trials, are needed to clarify the effectiveness of tDCS in bipolar depression, the frequency of tDCS-emergent hypomania/mania, and which tDCS modalities are most efficient.