How different pre-existing mental disorders and their co-occurrence affects clinical outcomes of COVID-19? A study based on real-world data in the Southern United States

Importance: A growing body of research focuses on the impact of pre-existing mental disorders on clinical outcomes of COVID-19 illness. Although a psychiatric history might be an independent risk factor for COVID-19 infection and mortality, no studies have systematically investigated how different clusters of pre-existing mental disorders may affect COVID-19 clinical outcomes or showed how the coexistence of mental disorder clusters is related to COVID-19 clinical outcomes. Objective: To explore how different pre-existing mental disorders and their co-occurrence affects COVID-19-related clinical outcomes based on real-world data. Design, Setting, and Participants: Using a retrospective cohort study design, a total of 476,775 adult patients with lab-confirmed and probable COVID-19 between March 06, 2020 and April 14, 2021 in South Carolina, United States were included in the current study. The electronic health record data of COVID-19 patients were linked to all payer-based claims data through the SC Revenue and Fiscal Affairs Office. Main Outcomes and Measures: Key COVID-19 clinical outcomes included severity, hospitalization, and death. COVID-19 severity was defined as asymptomatic, mild, and moderate/severe. Pre-existing mental disorder diagnoses from Jan 2, 2019 to Jan 14, 2021 were extracted from the patients healthcare utilization data via ICD-10 codes. Mental disorders were categorized into internalizing disorders, externalizing disorders, and thought disorders. Results: Of the 476,775 COVID-19 patients, 55,300 had pre-existing mental disorders. There is an elevated risk of COVID-19-related hospitalization and death among participants with pre-existing mental disorders adjusting for key socio-demographic covariates (i.e., age, gender, race, ethnicity, residence, smoking). Co-occurrence of any two clusters was positively associated with COVID-19-related hospitalization and death. The odds ratio of being hospitalized was 2.50 (95%CI 2.284, 2.728) for patients with internalizing and externalizing disorders, 3.34 (95%CI 2.637, 4.228) for internalizing and thought disorders, 3.29 (95%CI 2.288, 4.733) for externalizing and thought disorders, and 3.35 (95%CI 2.604, 4.310) for three clusters of mental disorders. Conclusions and Relevance: Pre-existing internalizing disorders, externalizing disorders, and thought disorders are positively related to COVID-19 hospitalization and death. Co-occurrence of any two clusters of mental disorders have elevated risk of COVID-19-related hospitalization and death compared to those with a single cluster.