Long-term trends in age at psychiatric admission (2006–2022): influence of sex, diagnosis, and admission type in a single Italian catchment

AIMS: Following Italy's psychiatric reform, national inpatient numbers declined, but how the age at admission has changed across sex, diagnostic, and admission-type subgroups remains unclear. This study examined 17 consecutive years (2006-2022) of psychiatric admissions to the sole ward serving L'Aquila, assessing temporal trends in age at admission by diagnosis, sex, and admission status (voluntary vs. compulsory). METHODS: All adult admissions (≥ 18 years) were extracted from hospital discharge records (Schede di Dimissione Ospedaliera, SDO). Analyses were conducted at the admission-episode level. Primary diagnoses were grouped into four ICD-9 categories: schizophrenia spectrum, major depressive disorder, bipolar disorder, and alcohol/substance use disorder. Multiple linear models tested time-related changes in mean age at admission, including interactions for time × diagnosis × sex × admission type. RESULTS: Across 5,207 admission episodes, the Trimester × Diagnosis interaction showed a marked decline in age at admission for major depression (B = - 0.20 per trimester, p < 0.001) and bipolar disorder (B = - 0.09, p = 0.03), equivalent to approximately - 0.80 and - 0.36 years per year, yielding total reductions of ~ 13.6 and ~ 6.1 years over 2006-2022. The Trimester × Diagnosis × Sex interaction indicated that the decline in depression was driven by men (B = - 0.32, p < 0.001; ≈ -1.28 years/year; -21.76 over 17 years), while in bipolar disorder it was driven by women (B = - 0.14, p = 0.03; ≈ -0.56 years/year; -9.52 over 17 years). The Trimester × Admission type interaction showed the reduction was specific to voluntary admissions (B = - 0.10, p < 0.001; ≈ -0.40 years/year), while compulsory admissions were stable (B = - 0.01, p = 0.87). No significant age change occurred in schizophrenia spectrum disorders or in alcohol/substance use disorders. CONCLUSIONS: Between 2006 and 2022, we observed a progressive rejuvenation of voluntary and affective-disorder inpatient admissions, with the clearest subgroup-specific reductions detected in men with major depression and women with bipolar disorder, while remaining stable in schizophrenia spectrum, alcohol/substance use disorder, and compulsory admissions. These findings underscore the need to balance youth-focused outreach with adequate capacity for chronic psychosis and substance use disorder.