Trends in Cannabis-Related and Opioid-Related Hospitalization Rates in Maine, 2010-2020

Introduction: Medical marijuana use became legal in the state of Maine in 1999, and recreational adult-use marijuana became legal in 2016. However, the rates of hospitalization related to marijuana (also known as cannabis) use have not been studied. We estimated trends in cannabis-related hospitalization rates in Maine based on rurality and descriptively compared these trends to opioid-related hospitalization rates during the past decade. Methods: We obtained de-identified data of inpatient encounters for Maine residents between 2010 and 2020 from MaineHealth Data Organization. We then calculated age-standardized rates of cannabis-related and opioid-related hospitalizations overall and by rural-urban residence using International Classification of Diseases clinical modification (ICD-CM) diagnosis codes. We used Poisson regression models to assess linear trends over time, stratified by ICD-9-CM versus ICD-10-CM timeframes. Results: Cannabis-related inpatient encounters accounted for 2.3% of all inpatient encounters among Maine residents between 2010 and 2020 and increased 0.3% per quarter between 2016 and 2020. Rates for urban residents were higher than rates for rural residents. Opioid-related inpatient encounters among Maine residents accounted for 3.4% of all inpatient encounters, and rates increased 0.6% per quarter between 2016 and 2020. Rates were higher among urban versus rural residents. Discussion: We found increasing rates of cannabis-related and opioid-related inpatient encounters in Maine spanning a period that included when recreational adult-use marijuana was legalized, but largely preceded its retail sales in Maine (October 2020). Conclusions: These trends and other public health impacts of increased access to marijuana use in Maine should continue to be monitored, especially after recreational adult-use marijuana is fully implemented.