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, age at admission declined steadily among voluntary affective-disorder cases—especially men with depression and women with bipolar disorder—while remaining stable among compulsory admissions, in schizophrenia spectrum and alcohol/substance use disorder admissions. Findings are compatible with a progressive rejuvenation of voluntary affective-disorder inpatient admissions, possibly reflecting earlier self-initiated help-seeking and/or evolving referral pathways, while underscoring the need to balance youth-focused outreach with adequate capacity for chronic psychosis and substance use disorder.