Structural neuroimaging markers in bipolar disorder

The diagnosis of mental disorders is strongly based on subjective reports of the patients and observations of behavior, and the determination of biomarkers for psychiatric disorders has been a long-lasting challenge. Structural neuroimaging techniques have been regarded as a potential tool to help improve diagnostic accuracy in psychiatry. This chapter displays a critical review of available evidence regarding structural neuroimaging findings in bipolar disorder (BD) and their potential diagnostic role. The main structural neuroimaging findings reported in BD are discussed, as well as neuroimaging features with the potential to distinguish BD from unipolar depressive disorders and schizophrenia. Although some results are consistently reported across different studies, the specificity of neuroimaging findings in mood disorders seems to be low. Therefore, despite the large amount of evidence available, differentiating BD from other psychiatric disorders, especially unipolar depression and schizophrenia, may be challenging, in part due to considerable phenotypical overlap across these conditions. As neuroimaging research continues to expand and new brain imaging techniques are created, it is reasonable to expect that new candidate biomarkers, with higher replication rates, will be identified.