The cost-of-illness of depression in 2023: analysis from a Japanese societal perspective including morbidity costs of employed individuals with recorded diagnosis

Quantifying the societal impact of diseases is vital for policymaking. Although Cost-of-Illness (COI) studies have been conducted globally, Japan has lacked an updated estimate of depression since 2008 owing to limited work productivity data. This study estimates the COI for depression in 2023 using Japanese work productivity data. A prevalence-based COI approach was applied from a societal perspective, comprising direct, morbidity, and mortality costs. Data sources included national statistics, model-based prevalence estimates, and Kencom, a patient-reported outcome database provided by DeSC Healthcare, Inc. The target population was adults aged ≥ 20 years diagnosed with depression (ICD-10: F32–F33). Annual days lost due to absenteeism and presenteeism were estimated using the Work Productivity and Activity Impairment (WPAI) questionnaire with depression diagnosis and other covariates adjusted using regression model analysis. A 2% discount rate was used to value mortality costs. The total societal cost of depression in 2023 was 1.6 trillion JPY (11.3 billion USD). Direct costs accounted for 224.2 billion JPY (1.6 billion USD). Morbidity costs were the largest component at 1.1 trillion JPY (7.8 billion USD), derived from model-adjusted productivity losses among employed individuals with recorded diagnosis based on 19,898 valid WPAI responses (844 with depression and 19,054 without) from the Kencom platform. Mortality costs totalled 277.9 billion JPY (2.0 billion USD). One-way sensitivity analysis showed that the prevalence was the most sensitive parameter; the total cost increased from 1,301 billion JPY (9.3 billion USD) to 1,969 billion JPY (14.0 billion USD). This is the first COI study of depression in Japan based exclusively on country-specific data, including productivity loss estimates. While these estimates involve uncertainty and limitations, the findings indicate a substantial and ongoing societal burden, with morbidity costs far exceeding direct medical and mortality costs.