Statistics
TD, schizophrenia
All the analyses were completed in SPSS version 23.0. Continuous baseline variables were compared between active and sham tDCS groups by independent sample t-test. Categorical variables were presented as frequency and compared by χ2 test. The primary objective of this study was to evaluate the effect of tDCS on cognitive function in chronic schizophrenia with TD. So the principal outcome was analyzed by repeated-measures analyses of variance with measurement time (baseline and weeks 3 and 5) as the within-group factor and active versus sham tDCS as the between-group factor. If the time × group interaction was significant, analysis of covariance (ANCOVA) was used to test for differences between groups at the end of weeks 3 and 5, with baseline score as the covariate. If the interaction was not significant, no further statistical tests were performed. The independent samples t-test was used to analyze changes in PANSS and SANS total scores. 