Phase‐based analysis of ICD‐10 psychiatric diagnoses in outpatients and inpatients after the 2024 Noto Peninsula Earthquake

Aim This study examined temporal changes in patterns of clinically treated psychiatric conditions during the first year after the 2024 Noto Peninsula Earthquake. Although post‐disaster psychiatric symptoms often peak within the first year, prior studies have frequently lacked standardized phase definitions. We applied disaster‐response phases defined in the Ministry of Health, Labour and Welfare manual to clarify phase‐specific diagnostic trends and inform allocation of psychiatric resources. Methods Among 869 new outpatients and 133 new inpatients recorded at Kanazawa Medical University Hospital, the tertiary medical center closest to the epicenter, between January and December 2024, we analyzed 80 first‐time outpatients and 29 newly admitted inpatients reporting earthquake‐related damage. Medical records were reviewed for demographics, ICD‐10 primary diagnoses, disaster‐related stressors, and timing of presentation categorized by disaster‐response phases. Results Psychiatric presentations were concentrated within the first month after the disaster, with secondary increases around 7 months and a modest rise at 12 months among outpatients. Most cases occurred during Stage 4 (mid‐term recovery; Months 2–12). Among outpatients, neurotic, stress‐related, and somatoform disorders (F4; 37.5%) and mood disorders (F3; 27.5%) were most frequent, whereas among inpatients, mood disorders (F3; 44.8%) and schizophrenia spectrum disorders (F2; 24.1%) predominated. Mood disorders were prevalent from the early phase, while F4 disorders increased later. Relocation and housing‐related problems were common stressors. Conclusion Clinically treated psychiatric conditions showed phase‐dependent patterns, underscoring the need for phase‐specific interventions, including early management of mood disorders, mid‐term support for displacement‐related stress, and long‐term monitoring for symptom re‐emergence.