Adjunct Bifrontal Transcranial Direct Current Stimulation in Improving Cognitive Insight and Working Memory Deficits in Schizophrenia: A Single-blind, Randomised Sham-controlled Trial.

Background: Cognitive deficits are an integral part of schizophrenia. This is a single-centre, single-blind randomised sham-controlled study to evaluate the effect of bilateral transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex on cognitive deficits in schizophrenia, specifically targeting improvements in cognitive insight and working memory deficits.

Method: Thirty patients with schizophrenia were randomly allocated to receive 10 sessions of bilateral tDCS (anodal F3 and cathodal F4) into active and sham tDCS groups. A series of assessment tests were completed among patients having Schizophrenia, at baseline and after the 10 sessions, for instance, Beck Cognitive Insight Scale (BCIS), N-Back (0' Back) task and Trail Making Test (TMT), Scale for Assessment of Positive Symptoms (SAPS), Scale for Assessment of Negative Symptoms (SANS) and Clinical Global Impression (CGI) scale.

Results: Out of a total of 30, twenty-seven participants (n = 13, Active and n = 14, Sham group) completed the study. However, an intention-to-treat analysis using Mixed model ANOVA was done on all the subjects. The study showed significant interaction effect (Time × Treatment) indicating that the active tDCS treatment had large effect on psychotic symptoms' reduction (SAPS: F(1,28) = 12.55, p = .001, partial η2 = 0.31; SANS: F(1,28) = 10.43, p = .003, partial η2 = 0.27) and significantly improved cognitive performance (N-Back Accuracy percentage: F(1,28) = 27.66, p < .001, partial η2 = 0.45; N-Back Reaction Time (in seconds): F(1,28) = 57.41, p < .001, partial η2 = 0.67). Furthermore, for cognitive insight, there was improvement in cognitive confidence (BCIS-C: F(1,28) = 5.43, p = .03, partial η2 = 0.16) and composite index (BCIS R-C: F(1,28) = 1.97, p = .17; partial η2 = 0.06) in Active vs. Sham group. TMT scores reduced more in the Active (-18.8s) as compared to the Sham group, suggesting better cognitive functioning, especially in the areas of attention, speed and mental flexibility (F(1,28) = 6.15, p = .02, partial η2 = 0.18).

Conclusion: The study suggests that the adjunctive bifrontal tDCS over DLPFC helps improve cognitive insight and working memory deficits among patients having schizophrenia.