Understanding the neurobiology of bipolar depression

Abstract

Despite the extensive research in the field, the precise etiology of bipolar disorder (BD) is not clear; neither, then, is our understanding of the pathogenesis of bipolar depression. What we do know is largely gleaned from investigations of patients with BD irrespective of their mood state. The most consistent neuropathological findings include structural, cellular, and functional changes in cortical and limbic regions, and most explanations for the illness involve pathways that ultimately result in cerebral atrophy and cell loss. Though many theories have been proposed, here, the focus is on the current leading hypotheses of mitochondrial involvement, oxidative stress, the role of inflammation, and neurotrophic factors. Future research is required with a specific focus on the depressive phase of BD in addition to the study of biomarkers to aid clinicians in the diagnosis and targeted treatment of bipolar depression.