Innovative approaches to hallucinations in psychosis and affective disorders: A focus on noninvasive brain stimulation interventions

Auditory verbal hallucinations (AVHs) are defined as verbal perceptions without an objective provoking external stimulus. AVHs are core symptoms of schizophrenia and psychotic spectrum disorders and have a wide prevalence in other severe psychiatric disorders including affective disorders and substance-use disorders. Despite adequate pharmacological treatment, AVHs can persist over the long-term course of these disorders in a significant percentage of patients, causing significant individual impairment. Noninvasive brain stimulation interventions represent a new frontier in the investigation and development of novel treatment options for both schizophrenia and psychotic spectrum disorders. In particular, transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) have been used in the treatment of AVHs in the last two decades. These techniques have the common feature of delivering electrical energy to the brain from an external source, as happens with tDCS, or through the induction of magnetic fields, as the case of repetitive TMS. The electrical stimulation is aimed to produce an excitation or inhibition of specific functional neuro-circuits that are involved in the pathogenesis of AVHs. In this chapter, we summarized main evidence in relation to the therapeutic use of the above-mentioned approaches in patients with AVHs, with specific attention to the recommendations of available international guidelines. Current major limitations and possible future perspectives are discussed as well