Role of rTMS in the treatment of cognitive impairments in Bipolar Disorder and Schizophrenia: a review of Randomized Controlled Trials

Background: Schizophrenia (SCZ) and Bipolar Disorder (BD) are severe psychiatric illnesses often characterized by mild-to-severe cognitive deficits. Since available pharmacotherapy showed poor efficacy in treating these cognitive impairments, new strategies are needed. Repeated Transcranial Magnetic Stimulation (rTMS) represents a safe non-invasive technique that has been hypothesized to improve cognitive symptoms in these pathologies. Therefore, our brief review aims at summarizing the results of Randomized Controlled Trials (RCTs) using rTMS for improving cognitive symptoms in SCZ and BD. Methods: We performed a bibliographic research on PubMed, Google Scholar and Medline of RCTs conducted in patients with BD and SCZ, which evaluated cognitive outcomes after rTMS treatment. Results: The inclusion criteria were met by fifteen RCTs, twelve in SCZ and three in BD. Regarding patients with SCZ, the results showed that rTMS seemed to have poor effects on improving cognitive performances, with mixed results also observed for schizoaffective patients. In BD, overall the RCTs showed that rTMS in these patients seemed to improve cognitive domains in euthymic patients, while its effect during acute phases, especially depression, appeared limited. Limitations: Studies employed different rTMS protocols and evaluated different cognitive domains. Conclusions: Although the available evidence from RCTs evaluating the efficacy of rTMS on cognitive deficits in SCZ and BD are still mixed and heterogenous, overall they suggest that rTMS represents a potential clinical tool that could ameliorate cognitive symptoms, especially in specific patients’ subtypes. However, standardized protocols and further research are still necessary to evaluate the real efficacy of rTMS.