Comparison of Mental Illness Comorbidity Pre-Pandemic vs. Pandemic-Era and Associations with Clinical and Demographic Characteristics for Virginia Public Hospital Inpatient Discharges with a Substance Use Disorder

The rise in mental illnesses after the COVID-19 pandemic is well documented. However, it is not known whether the rates of mental illness comorbidity increased. The objectives of this study were to compare mental illness comorbidity rates before and after the pandemic among inpatients with SUD and to test associations between mental illness comorbidity, physical illness, and demographics. We used a retrospective cross-sectional design in a sample of inpatient discharges (N = 233,017) at Virginia public hospitals from January 2018 to December 2022. We used Z tests to compare rates of mental illness comorbidity pre- and post-pandemic and Chi-square tests to examine associations of mental illness comorbidity with physical illness and demographics. Single and comorbid mental illness significantly increased from pre- to post-pandemic, <i>p</i> < 0.0001. Mental illness comorbidity was significantly associated with sex, age, race, insurance, COVID-19/Long COVID, HIV/AIDS, COPD, hypertension, obesity, CVD, cancer, and diabetes (<i>p</i> < 0.0001). There was a significant increase in mental illness comorbidity, which was significantly associated with age, race, sex, and physical illnesses. Children/adolescents, females, American Indians, and individuals with HIV/AIDS had the highest rates of mental illness comorbidity. Public health action is needed to address the increase in complex medical needs among people with SUD.