Chronic Disease Management Among People Treated for Comorbid Serious Mental Illness and/or Substance Use Disorders: A Population-Based Observational Study

People with serious mental illness and/or substance use disorders are at high risk of chronic physical diseases like diabetes and hypertension and related acute complications but may face barriers to chronic disease management (including medication management and laboratory testing). We describe patterns of service use and chronic disease management among people with diabetes and/or hypertension treated for comorbid serious mental illness and/or substance use disorders. We used linked British Columbia administrative health data from April 1, 2020 to March 31, 2022 to conduct a retrospective cohort study among adults with diabetes and/or hypertension and used standardized differences to compare how health service use and chronic disease management varied for those treated for comorbid serious mental illness and/or substance use disorders. People treated for comorbid serious mental illness and/or substance use disorder had high service use (more primary care visits, ED visits, and hospitalizations) but received less recommended lab testing and medication management for diabetes or hypertension. These findings show people treated for serious mental illness and/or substance use disorders receive inequitable chronic disease management, despite frequent primary care use. Reshaping care to address underlying barriers will be crucial to improving chronic disease management in this population.