Novel biomarkers for bipolar disorder.

INTRODUCTION: Bipolar disorder is diagnosed on the basis of patient and/or family reports and behavioral observation. Traditionally regarded as an affective disorder involving behavioral changes, bipolar disorder has been reconceptualized as a multisystem disease associated with mood, cognitive, metabolic, autonomic and sleep/wake dysfunctions. Accordingly, recent studies have focused on the identification of biomarkers related to the pathophysiological mechanisms underlying the development, clinical presentation and course of bipolar disorder. AREAS COVERED: This article provides an overview of the available literature regarding circulating peripheral and neuroimaging biomarkers in bipolar disorder. Neurotrophic factors, immune parameters, oxidative stress parameters, hormones and neuroimaging findings were taken into consideration. EXPERT OPINION: Biomarkers research in bipolar disorder is a new field with an expanding knowledge. Current evidence suggests that a single biomarker will not be able to cover the biological and clinical complexity of bipolar disorder. Alternatively, a composite of biomarkers, including neurotrophic factors, cytokines and oxidative stress molecules, may be promising to identify altered mood states and neuroprogression in bipolar disorder.