Abstract
BACKGROUND AND HYPOTHESIS: Impaired insight into illness affects up to 95% of individuals with schizophrenia, depending on the stage of illness, and is a predictor of antipsychotic nonadherence and poor clinical outcomes. Despite its importance, no effective treatment exists. Interhemispheric imbalance in frontoparietal regions may serve as a biomarker of impaired insight into illness and target for transcranial direct current stimulation (tDCS). Meta-analyses suggest that sham-controlled multisession tDCS applied to frontotemporoparietal areas improves insight in schizophrenia. However, no randomized controlled tDCS trial has targeted the posterior parietal areas to improve insight into illness. We hypothesized that multisession biparietal tDCS would lead to both immediate (ie, following 2-weeks of tDCS) and sustained (ie, up to 4-weeks) improvement in insight in schizophrenia. STUDY DESIGN: Thirty-four participants with schizophrenia/schizoaffective disorder and impaired insight into illness were randomized to receive either active (n = 18) or sham (n = 16) biparietal tDCS (anodal/cathodal:P4/P3), administered twice daily over 10 days. Insight was assessed using the VAGUS Insight into Psychosis scale at baseline pre-treatment, post-treatment, and weekly for 4 weeks. Linear mixed-effects models compared estimated marginal mean VAGUS scores between conditions, with and without adjusting for Intelligence Quotient (IQ), illness severity, and clozapine use. STUDY RESULTS: Active tDCS significantly improved average VAGUS scores immediately following and up to 4 weeks post-treatment. CONCLUSIONS: Biparietal tDCS appears to be a promising intervention for improving insight in schizophrenia. Future research should explore its adjunctive use with medication to enhance treatment adherence.