Transcranial Magnetic Stimulation (TMS) as a treatment tool in schizophrenia: A review.
Schizophrenia is a chronic, debilitating psychiatric disorder that has an immense impact on the patients, their families, and the entire society. Schizophrenia is characterized by positive symptoms (e.g., hallucinations, delusions), negative symptoms (e.g., apathy, reduced emotional response), as well as a variety of cognitive dysfunctions. While positive symptoms are often successfully treated with antipsychotic medications, negative symptoms and cognitive impairments tend to be more treatment refractory. Moreover, the occurrence of persistent, systemic side effects in schizophrenia patients taking antipsychotic medications significantly affects their compliance. Thus, more targeted, symptom-specific treatment interventions are critically needed in schizophrenia. Transcranial Magnetic Stimulation (TMS) allows to directly and noninvasively reach the cortical surface. TMS can therefore target specific cortical areas, which are involved in some of the symptoms or cognitive dysfunctions commonly experienced by schizophrenia patients, while at the same time minimizing systemic side effects. Furthermore, it has been shown that repetitive stimulation (rTMS) delivered at low frequency (≤ 1 Hz) or high frequency (>1 Hz) can respectively increase or decrease neural excitability, including the brain regions involved in the pathophysiology of schizophrenia. Because of these unique features, over the past two decades there has been a burgeoning of studies investigating rTMS as a treatment tool in schizophrenia. In this review, we will systematically analyse these data, focusing on studies that examined the effects of rTMS on positive, negative and cognitive symptoms. Specifically, we will present main findings from these rTMS studies, highlight their strengths and pitfalls, and we will then discuss how these findings may contribute to develop more effective, TMS-based treatment interventions in schizophrenia.