Japanese Study Reveals Treatment‐Resistant Schizophrenia Prevalence in Inpatients

Key Takeaways

• Among hospitalized patients with schizophrenia at participating clozapine-authorized institutions in Japan, 28.6% of those examined were classified as having TRS.
• A documented TRS examination was recorded for 52.2% of the overall inpatient cohort.
• Clozapine was prescribed at discharge for 46.4% of patients classified as having TRS.

Hospitalized patients with schizophrenia were evaluated in Arai and colleagues’ nationwide multicenter observational study, which used Japanese data collected annually from 2016 to 2024 through the Effectiveness of Guidelines for Dissemination and Education in Psychiatric Treatment (EGUIDE) project. The cohort comprised 18,914 patients hospitalized for at least 4 days and discharged from 205 EGUIDE-participating institutions accredited to prescribe clozapine.

Participating psychiatrists were trained in standardized Japanese TRS criteria and instructed to record assessments in discharge summaries. The Japanese Clozapine Appropriate Use Committee criteria encompass poor response or poor tolerability. TRS prevalence was calculated only among evaluated patients; clozapine prescribing at discharge was calculated among patients identified with TRS. Age and institution type were compared according to whether an examination was documented.

A documented TRS examination was recorded for 9,870 patients, while 9,044 had no examination recorded. Among those evaluated, 2,819 were classified as having TRS under the Japanese criteria. Patients without a documented examination did not contribute to the prevalence calculation.

Among patients classified with TRS, 1,307 had a clozapine prescription recorded at discharge. Patients with a documented TRS examination were significantly younger on average than those without one. Institution type also differed significantly: university and private hospitals were more represented among examined patients, whereas public hospitals were more represented among those not examined.

Hospitalized patients discharged from EGUIDE institutions authorized to prescribe clozapine may not represent all people with schizophrenia in Japan. The authors cautioned that incomplete TRS evaluation and differences in institution type between examined and unexamined patients could make the prevalence estimate reflect those selected for assessment.

Clinician Questions

Does the Japanese estimate of treatment-resistant schizophrenia prevalence apply to outpatients?

Arai and colleagues studied discharged hospital patients with schizophrenia at EGUIDE-participating Japanese institutions licensed to prescribe clozapine, not outpatients. The authors cautioned against extending the estimate to the broader Japanese population with schizophrenia, particularly outpatients.

Does clozapine prescribing at discharge show treatment benefit in Japanese inpatients with treatment-resistant schizophrenia?

Among Japanese hospitalized patients classified with treatment-resistant schizophrenia, the clozapine finding records whether a prescription was documented at discharge; it does not measure clinical response, treatment effectiveness, or improvement.