Bipolar disorders

In the last decades, researchers put their efforts in searching for specific biomarkers to make the diagnosis of psychiatric disorders more accurate, to better profile psychiatric patients, and, essentially, to improve their response to treatment and their outcome. This is particularly important in the field of bipolar disorders (BDs), which are severe and chronic disorders with polymorphic clinical manifestations that may be the expression of different underlying neurobiological alterations. Currently, neuroimaging techniques are considered an essential tool for the noninvasive evaluation of putative brain dysfunctions of these patients. Neuroimaging studies aim to find brain alterations associated with the diagnosis of BD or with some psychopathological dimensions (such as mood lability, emotional instability, etc.) specific of BD patients. These findings should improve the understanding of the mechanisms underlying the disorder and may become potential targets of pharmacological and non-pharmacological treatment (i.e., neurocognitive rehabilitation). This chapter aims at providing an exhaustive review of the studies on brain morphology in bipolar disorder in order to better characterize it from a neurobiological point of view, thus providing a comprehensive background for further research on this topic. Structural abnormalities were found in regions pertaining to specific networks postulated as vulnerable in BD. Specifically, alterations in the neocortical areas of the brain, in particular the frontotemporal circuit, and in subcortical areas of the brain have been identified. In general, the findings suggest that it is necessary to consider large-scale neural circuitries more than specific brain structures to understand the neurobiological mechanisms underlying BD. Moreover, our review points up the need for longitudinal studies that might better investigate, and cast light on, these issues.