The Impact of Mental Health Comorbidities on Unplanned Admissions for Physical Conditions: A Retrospective Observational Analysis.

: This study aimed to evaluate the impact of mental health comorbidities on unplanned hospital admissions (UHAs) in the Province of Pescara, Southern Italy, during 2015-2022. Mental health comorbidities are underreported in administrative data, yet their association with UHAs has significant public health implications. : A retrospective observational design was used to analyze 59,374 hospital admissions extracted from hospital discharge records (HDRs). Admissions of patients under 18 years of age, deliveries, day admissions, and readmissions were excluded. Socio-economic deprivation was assessed using a standardized deprivation index. Multivariate logistic regression analyzed the association between UHAs and mental health comorbidities, adjusting for socio-demographic and clinical factors. : Of the 59,374 admissions, 43,293 (72.9%) were unplanned. Mental health comorbidities had a low prevalence (1552 cases, 2.6%) but were significantly more common in UHAs (3.4%) compared to planned admissions (0.4%, < 0.001). UHAs were also associated with the female gender (OR = 1.10; 95% CI: 1.06-1.14), younger age categories, living in less deprived areas, two or more physical comorbidities (OR = 1.66; 95% CI: 1.56-1.75), and mental health comorbidities (aOR = 9.85; 95% CI: 7.74-12.55, < 0.001). : Mental health comorbidities significantly increase the risk of UHAs independent of socio-economic deprivation or physical comorbidities. These findings underscore the need for enhanced mental health management to reduce UHAs, improve patient outcomes, and address healthcare inequities.