Abstract: Objective:To measure the direct and indirect costs of major depressive disorder (MDD) and bipolar disorder (BD), and to explore the drivers of the total costs. Methods:A total of 230 inpatients with MDD and BD recruited from a Seconary Grade A psychiatric hospital in Tongling City from May 2019 to July 2021 were selected. Inpatient's total outpatient and inpatient medical costs, out-of-pocket costs, and non-medical costs in the past year were collected as direct costs, and productivity loss caused by the patient's inability to work and other losses caused by damaging properties due to disease were defined as indirect costs. Direct and indirect costs were calculated at individual and societal levels. Multiple linear regression model was applied for detecting the influencing factors of disease costs. Results:The total cost of MDD was higher than that of BD at individual level, but the total cost of BD was higher than that of MDD at societal levels. The indirect costs of two mental disorders were higher than the direct costs. Multiple linear regression analysis showed that working condition, marital status, income, and disease severity were associated drivers of total costs. Conclusion:The economic burden of the two mental disorders is heavy, and the productivity loss due to mental disorders is the driving force of the disease cost.