Prescription Trends of Kampo Medicines in the Department of Psychiatry at a University Hospital: A 12-Year Retrospective Study

Aim: Kampo medicines are widely integrated into Japanese healthcare, yet long-term prescription trajectories and sex-associated patterns in psychiatric outpatient settings remain poorly characterized.This study aimed to evaluate workload-standardized prescription trends and sex-specific utilization patterns of Kampo extract formulations at a university hospital psychiatric department over a 12-year period.Methods: Electronic medical record prescription data of psychiatric outpatients at Kyoto University Hospital, Kyoto, Japan, were retrospectively analyzed.Longitudinal trends in raw prescription counts and workload-standardized rates per 1,000 outpatient visits were evaluated using simple linear regression.Sex differences in formulation distribution were assessed using Chi-square tests of independence, odds ratios with 95% confidence intervals, and the Shannon Diversity Index.Demographic distributions were categorized into 10-year age brackets.Results: Workload-standardized prescription rates per 1,000 outpatient visits more than doubled from 7.09 in financial year (FY) 2011 to 15.08 in FY 2022 (R 2 = 0.882, p < 0.001; raw counts: 245 to 386, peaking at 387 in FY 2019).Yokukansan was the most prescribed formula overall (19.0%, n = 705).Overall formulation choices differed significantly between sexes (p < 0.001).Male outpatients exhibited significantly higher odds of receiving Yokukansan than females (27.9% vs. 14.5%, p < 0.001).Conversely, female patients demonstrated greater overall formula diversity (H' = 3.01 vs. 2.59) and higher proportions of Kamishoyosan (7.4%) and Tokishakuyakusan (4.8%).Working-age adults (20-59 years) constituted 71.8% (n = 2,667) of total prescriptions, while outpatients aged 70 years represented 11.8% (n = 440).Conclusion: Kampo pharmacotherapy has steadily expanded in university psychiatric outpatient care.Prescribing practices demonstrate distinct sex-associated variations, characterized by a male preference for Yokukansan and broader formulation diversity in female patients.Given the high concentration among working-age adults, these patterns extend beyond geriatric care, though residual age-related confounding cannot be entirely excluded.Because diagnostic codes were not evaluated, these observations reflect pragmatic real-world prescribing behaviors rather than verified therapeutic efficacy, offering a robust empirical baseline for future diagnostic-linked prospective studies.