Although the etiology of
bipolar disorder remains uncertain, multiple studies examining neuroimaging, peripheral markers and genetics have provided important insights into the pathophysiologic processes underlying
bipolar disorder. Neuroimaging studies have consistently demonstrated loss of gray matter, as well as altered activation of subcortical, anterior temporal and ventral prefrontal regions in response to emotional stimuli in
bipolar disorder. Genetics studies have identified several potential candidate genes associated with increased risk for developing
bipolar disorder that involve circadian rhythm, neuronal development and
calcium metabolism. Notably, several groups have found decreased levels of
neurotrophic factors and increased pro-inflammatory
cytokines and oxidative stress markers. Together these findings provide the background for the identification of potential
biomarkers for vulnerability, disease expression and to help understand the course of illness and treatment response. In other areas of medicine, validated
biomarkers now inform clinical decision-making. Although the findings reviewed herein hold promise, further research involving large collaborative studies is needed to validate these potential
biomarkers prior to employing them for clinical purposes. Therefore, in this positional paper from the ISBD-BIONET (
biomarkers network from the International Society for
Bipolar Disorders), we will discuss our view of
biomarkers for these three areas: neuroimaging, peripheral measurements and genetics; and conclude the paper with our position for the next steps in the search for
biomarkers for
bipolar disorder.