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The efficacy of transcranial direct current stimulation in improving cognitive functioning in depression: A meta-analysis
Abstract

The efficacy of transcranial direct current stimulation in improving cognitive functioning in depression: A meta-analysis

R S C Lee, D Martin, M Kaur, I B Hickie and Jim Lagopoulos
Brain Stimulation, Vol.8(2), p.421
International Brain Stimulation Conference, 1st (Singapore, 01-Mar-2015–04-Mar-2015)
2015
DOI: https://doi.org/10.1016/j.brs.2015.01.344
url
https://doi.org/10.1016/j.brs.2015.01.344View
Published Version

Abstract

Medical and Health Sciences
Background: Evidence is emerging demonstrating the efficacy of transcranial direct current stimulation (tDCS) in the treatment of depression. However, whether tDCS is also efficacious in promoting lasting cognitive improvement remains unclear, despite evidence of cognitive enhancement after just one session. Here we sought to conduct a meta-analysis on randomized, double-blind, shamcontrolled trials of tDCS in depressive disorders. Methods: Electronic databases were searched for studies published between January 2006 and November 2014. Seven independent active tDCS samples from 6 studies met eligibility criteria (total N ¼ 142, mean age ¼ 46.8 years), and were each compared with respective sham tDCS samples (total N ¼ 140, mean age ¼ 46.4 years). All studies delivered anodal stimulation to the left dorsolateral prefrontal cortex (F3) for between 5 and 15 sessions, and currents ranged from 1 to 2 mA. Three studies placed the cathode over the lateral aspects of the contralateral orbits, whereas the others used the supraorbital region. Results: Compared with sham tDCS, active tDCS participants improved across psychomotor speed, attention span, working memory, and response inhibition, whereas verbal fluency and attentional set-shifting improved more after sham tDCS. Each pooled ES, however, was in the very small range ( 0.0-0.19), and all non-significant (p > 0.05). There was no evidence of significant heterogeneity across studies, or publication bias (all p > 0.05). Conclusions: There is limited evidence to suggest that tDCS as currently employed (electrical current strength, frequency/duration of delivery) is effective in promoting cognitive recovery in depressive disorders. Most studies have used small samples, not co-varied for mood improvement, and focused on recurrent-episode and middle-aged cohorts. Future studies may benefit from adjunctive treatments specifically developed to improve neuropsychological functioning, such as cognitive training, and should consider targeting recent-onset individuals in which cognitive deficits may be less entrenched and potentially more responsive to treatment.

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