Bipolar disorder (BD) is a mood disorder with subtypes characterized by episodes of mania, hypomania, and/or depression. BD is associated with substantial economic burden, and the bipolar I disorder (BD-I) subtype is associated with high medical costs. This review further evaluated the economic burden of BD and BD-I in the United States (US), describing health-care resource utilization (HCRU) and sources of direct medical and indirect costs. Data were obtained from systematic searches of MEDLINE, EMBASE, and National Health Service Economic Evaluation Database. Citations were screened to identify primary research studies (published 2008-2018) on the economic burden of BD/BD-I or its treatment in real-world settings. Reported costs were converted to 2018 US dollars. Of identified abstracts (N=4111), 56 studies were included. The estimated total annual national economic burden of BD/BD-I was more than $195 billion, with approximately 25% attributed to direct medical costs. Individuals with BD/BD-I used health-care services more frequently and had higher direct medical costs than matched individuals without the disease. Drivers of higher direct costs included frequent psychiatric interventions, presence of comorbid medical/psychiatric conditions, and both suboptimal medication adherence and clinical management. Indirect costs (eg, unemployment, lost work productivity for patients/caregivers) accounted for 72-80% of the national economic burden of BD/BD-I. Different definitions for study populations and cost categories limited comparisons of economic outcomes. This review builds on existing literature describing the economic burden of BD and confirmed cost drivers of BD/BD-I. Improved clinical management of BD/BD-I and associated comorbidities, together with better medication adherence, may reduce health-care costs and improve patient outcomes.© 2020 Bessonova et al.