Depressive and anxiety symptom trajectories in psychiatric inpatients with nosocomial infection: a retrospective study from China.

Background: Psychiatric inpatients are particularly vulnerable to nosocomial infections (NIs) due to cognitive impairment, impaired self-care, and closed ward environments. This study aimed to characterize the epidemiological and pathogen profile of NI, examine the trajectory of depressive and anxiety symptoms during hospitalization, identify risk factors for non-respiratory infections, evaluate the role of companion caregivers, and quantify the economic burden attributable to NI in a psychiatric hospital setting. Methods: A retrospective analysis was conducted on 79 NI cases from a psychiatric hospital in China (March 2022 to June 2025). Data included demographics, infection characteristics, hospitalization cost, and paired Hamilton Depression Rating Scale (HAMD) and Hamilton Anxiety Rating Scale (HAMA) scores at admission and before discharge. Statistical analyses included chi-square tests, t-tests, Wilcoxon signed-rank tests, Mann-Whitney U tests, and multiple linear regression. Results: Respiratory tract infections predominated (60/79, 75.95%). Females had significantly higher non-respiratory infection rates than males (16/44, 36.36% vs 3/35, 8.57%, chi-square=6.792, P = 0.009), and companion-accompanied patients had higher non-respiratory infection rates than those without companions (14/40, 35.00% vs 5/39, 12.82%, chi-square=4.173, P = 0.041). Paired analysis revealed significant improvement in both depressive (HAMD change: -7.00 ± 10.60, paired t=2.723, P = 0.015; Wilcoxon P = 0.015; Cohen's d=0.66) and anxiety symptoms (HAMA change: -4.19 ± 6.32, paired t=2.652, P = 0.018; Wilcoxon P = 0.029; Cohen's d=0.66) from admission to discharge, though residual symptoms persisted. Each additional day of NI duration was associated with an additional 730.79 CNY in total hospitalization cost. Multiple regression for cost prediction yielded R²=0.774. Mycoplasma pneumoniae was the most frequently identified pathogen (14/79, 17.72%), while 53.16% of cases had no pathogen identified. Conclusions: Preliminary evidence suggests NI is associated with elevated psychiatric symptom burden at admission and significant symptom improvement during hospitalization, though residual symptoms persist. Without a non-infected control group, directionality cannot be established. Companion-accompanied patients represent a high-risk subgroup with elevated psychiatric symptom burden and distinct infection patterns. NI duration was independently associated with increased hospitalization costs. These findings highlight the need for integrated infection-psychiatric management protocols in psychiatric hospitals.