High-definition transcranial direct current stimulation for treating cognitive and negative symptoms in chronic schizophrenia – A sham-controlled proof of concept study

Abstract

Objectives: Cognitive and negative symptoms are core symptoms of schizophrenia affecting interpersonal and socio-occupational functioning. Impaired dorsolateral prefrontal cortex (DLPFC) function is implicated in negative and cognitive symptoms. Conventional transcranial direct current stimulation (tDCS) to DLPFC has attracted interest as an add-on treatment for these symptoms. High-definition tDCS (HD-tDCS), an optimized form of tDCS, has the potential for more focalized neuromodulation. Studies suggest that an increased number of sessions may increase the effectiveness of stimulation. Hence, we aimed to evaluate the efficacy of 20 sessions of HD-tDCS over the left DLPFC in the improvement of cognitive and negative symptoms in chronic schizophrenia (>2 years continuous illness). Material and Methods: Twenty patients with chronic schizophrenia with predominantly cognitive and negative symptoms were enrolled in this sham-controlled trial. Participants received 20 sessions of HD-tDCS at 2 mA for 20 min, that is, twice daily over 10 days. Montreal cognitive assessment and scale for assessment of negative symptoms were used to assess outcome variables. Assessments were carried out at baseline, 2 weeks, and 6 weeks, respectively. Results: Significant improvement was noted in both active and sham groups across all outcome variables over time. However, a statistically significant decrease in negative symptoms in the active group was noted, which was maintained at the end of 6 weeks, but there was no statistically significant improvement in cognitive symptoms between the active and sham groups at 6 weeks. The stimulation protocol was well tolerated. Conclusion: HD-tDCS has substantial potential in the treatment of negative symptoms; however, its role in cognitive symptoms needs further evaluation.