The role of marijuana use disorder in predicting emergency department and inpatient encounters: A retrospective cohort study

Background: Marijuana use disorder (MUD) is the most common illegal drug use disorder and its prevalence is increasing. It is associated with psychiatric and medical problems, but little is known about its impact on emergency department (ED) and inpatient utilization rates. Design: In a retrospective cohort design, we used electronic health record (EHR) data to identify patients with MUD (n = 2752) and demographically matched patients without MUD (n = 2752) in 2010. Logistic regressions determined risk of ED and inpatient visits each year from 2010 to 2014 for MUD patients versus controls; mixed effect growth models examined differences in utilization rates over 5-years. Patient characteristics predicting increased risk of utilization were examined among the MUD sample only. Key results: Rates of ED (OR = 0.87, p < 0.001) and inpatient (OR = 0.76, p < 0.001) services use significantly declined over 5 years for all patients. Patients with MUD exhibited a significantly greater decline in ED (OR = 0.81, p < 0.001) and inpatient (OR = 0.64, p < 0.001) use relative to controls. However, MUD patients had significantly greater risk of having ED and inpatient visits at each time point (p's < 0.001). MUD patients with co-occurring other substance use, medical, and/or psychiatric disorders had a greater risk of having ED or inpatient encounters over 5 years (p's < 0.001). Conclusions: MUD patients remain at high risk for ED and inpatient visits despite decreasing utilization rates over 5 years. Addressing MUD patients' comorbid conditions in outpatient settings may help reduce inappropriate service use.