Antidepressant initiation after sublingual immunotherapy in Japanese cedar pollinosis: a real-world propensity score-matched cohort study.

OBJECTIVE: To evaluate whether sublingual immunotherapy (SLIT) for Japanese cedar pollinosis is associated with subsequent initiation of antidepressants, and to assess its clinical implications for mental health management in real-world clinical practice. METHODS: We conducted a retrospective real-world cohort study using a large nationwide administrative claims database in Japan from 2014 to 2021. Adult patients diagnosed with Japanese cedar pollinosis were identified and classified as SLIT users or non-users using a new-user design. Propensity score matching was performed to balance patients' baseline characteristics, including age, sex, insurance type, and medical history. The primary outcome was initiation of antidepressant prescriptions. Hazard ratios were estimated using matched cohorts. RESULTS: A total of 4,126 SLIT users and 88,455 non-users were identified, with 3,991 propensity-matched patients in each group. Before matching, mental disorders were more prevalent among SLIT users than among non-users, whereas allergic rhinitis severity was similar between groups. Crude initiation rates of antidepressants were 5.0 and 2.9 per 1,000 person-years among SLIT users and non-users, respectively. After matching, no statistically significant association was observed between SLIT use and antidepressant initiation (hazard ratio = 1.11, 95% confidence interval = 0.73-1.69). Kaplan-Meier analysis also showed no significant between-group differences. CONCLUSION: No statistically significant association was observed between SLIT for Japanese cedar pollinosis and antidepressant initiation. These findings suggest that mental health outcomes should continue to be monitored independently of immunotherapy use in routine clinical practice. Further adequately powered studies with longer follow-up periods are warranted to better characterize depressive outcomes in this population.