Adjunctive transcranial direct current stimulation for cognitive improvement in schizophrenia: insights from a systematic review and exploratory meta-analysis

Gaolei Yao¹Yuan Huang²Junjiao Ping³Liming Lu^1*Xinxia Liu^3*Huipeng Lu^3*

• ¹Clinical Research and Big Data Laboratory, South China Research Center for Acupuncture and Moxibustion, Medical College of Acu-Moxi and Rehabilitation, Guangzhou University of Chinese Medicine, Guangzhou, China
• ²Department of Acupuncture, Shaoguan Hospital of Traditional Chinese Medicine, Shaoguan, China
• ³Department of Psychiatry, Third People's Hospital of Zhongshan City, Zhongshan, Guangdong Province, China

Introduction: To objectively and accurately evaluate the clinical efficacy of transcranial direct current stimulation (tDCS) for schizophrenia, we conducted this systematic review and exploratory meta-analysis (PROSPERO: CRD420251002632).Methods: Firstly, randomised controlled trials (RCTs) related to the adjunctive use of tDCS for schizophrenia were searched on PubMed, Embase and Web of Science databases according to search strategies developed in advance. Secondly, the eligible articles were screened according to the inclusion and exclusion criteria. Finally, the data were extracted and a complete meta-analysis was performed. Meanwhile, we also completed publication bias analysis and sensitivity analysis. Statistical analysis was conducted using RevMan software (version 5.4).Results: We ultimately included 11 eligible RCTs. The results of the exploratory meta-analysis indicated that the adjunctive use of tDCS seems to be able to enhance the cognitive function of patients (the Paced Auditory Serial Addition Task: standardized mean deviation (SMD) = 3.57, 95% confidence interval (CI) (2.60, 4.54), P < 0.00001). Subgroup analyses showed that the adjunctive use of tDCS at 15 sessions (Clinical Global Impression-Schizophrenia scale: SMD= -0.56, 95% CI (-0.87, -0.25), P=0.0004) or twice daily (Clinical Global Impression-Schizophrenia scale: SMD= -0.85, 95% CI (-1.67, -0.03), P=0.04) also decreased the disease severity.Discussion: This exploratory meta-analysis revealed that tDCS in the treatment of schizophrenia appears capable of improving cognitive function and effectively reducing the severity of the disease. What’s more, tDCS has great development potential in schizophrenia, and it may be written into the guidelines for non-drug treatment of schizophrenia in the future. As a matter of fact, this exploratory study points out the direction for future scientific research and clinical practice.