Rate of subsequent emergency department and inpatient hospital visits among individuals with cannabis‐associated diagnoses: A retrospective cohort study of Arizona, USA hospital discharge data

AIMS: To track people with a cannabis-associated diagnosis during a hospital visit and examine rates of subsequent hospital visits over one year, including visits with mental health- and substance use-associated diagnoses. DESIGN: Retrospective cohort study of Arizona, USA hospital discharge data. Patients were observed for one year before and after their 2018 index visit to capture hospital encounters with mental health- and substance use-associated diagnoses. SETTING: Data were patient-level emergency department and inpatient hospital records from Arizona, USA 2017-2019. PARTICIPANTS: Four groups of patients were identified based on diagnoses during their index visit in 2018. These included people who had 1) a cannabis-associated diagnosis and a co-occurring mental health-associated diagnosis (C+/MH+; n = 16 699), 2) a cannabis-associated diagnosis but not a mental health-associated diagnosis (C+/MH-; n = 21 406), 3) a mental health-associated diagnosis but not a cannabis-associated diagnosis (C-/MH+; n = 230 519), and 4) neither a cannabis-associated nor a mental health-associated diagnosis (C-/MH-; n = 1 096 939). MEASUREMENTS: Records included diagnosis codes from the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM), which were used to identify cannabis-associated diagnoses, other substance use-associated diagnoses, and mental health-associated diagnoses. In analyses predicting subsequent hospital visits, covariates included demographic factors; index visit month; total number of past-year visits, visits with a mental health-associated diagnosis, and visits with a substance use-associated diagnosis; concurrent (to the index visit) non-cannabis substance use-associated diagnosis and the Elixhauser readmission index. RESULTS: After adjusting for covariates, people with a cannabis-associated diagnosis during their index visit in 2018 had 1.23 times the rate of subsequent hospital visits as those without a cannabis-associated diagnosis (99.8% confidence interval (CI) [1.20, 1.26]), 2.74 times the rate of subsequent visits with a mental health-associated diagnosis (99.8% CI [2.64, 2.84]), and 1.76 times the rate of subsequent visits with a substance use-associated diagnosis (99.8% CI [1.69, 1.83]). Elevated visit rates were observed among individuals with a cannabis-associated diagnosis, regardless of whether they had a concurrent mental health-associated diagnosis, though associations were stronger among those without a concurrent mental health-associated diagnosis. SUMMARY: A cannabis-associated diagnosis during a hospital visit appears to signal risk for higher rates of subsequent hospital use.