To measure the population level association of mental health disorders with in-hospital mortality among patients with a diagnosis of encephalitis and to compare baseline characteristics between encephalitis  patients with and without mental disorders.

Studies have shown following encephalitis, cognitive deficits and psychiatric symptoms manifesting among patients is common and that greater care for these symptoms is needed following treatment for encephalitis, suggesting a relationship between encephalitis and mental health disorders. Literature has shown that a lower Glasgow Come Scale (GCS) score is associated with higher mortality rates. However, the impact of pre-existing mental health disorders preceding encephalitis on outcomes of the patient has not been extensively studied.

We conducted a population-based cohort study of adults admitted to intensive care units at acute care hospitals in Texas with a diagnosis of encephalitis during 2016-2022.  Hospitalizations with a diagnosis of encephalitis were identified with the aid of Clinical Classification Software Refined category NVS002:Encephalitis. The primary exposure was diagnosis of pre-existing mental disorder.  Propensity-adjusted multilevel logistic regression was used to test the association of mental disorders and in-hospital mortality. Subgroup and sensitivity analyses included demographics, types of mental disorders, type of admission, and principal diagnosis of encephalitis. Results are reported as adjusted odds ratio and 95% confidence interval (aOR 95%CI).

A total of 15,771 hospitalizations were identified with 4,327(27.4%) having mental disorders. Hospitalizations with mental disorders were younger, more often female, and more often White. In-hospital mortality was 4.6% for patients with mental disorders and 9.8% for patients without mental disorders. Mental disorders remained associated with mortality on adjusted analyses aOR 0.6770 (0.5614 - 0.8165). The results were consistent on subgroup, sensitivity and alternative analyses.

Hospitalizations with mental disorders are associated with substantially reduced in-hospital mortality. Further studies are needed to understand the role of mental disorders in the outcomes of encephalitis hospitalizations.