Changes in Emergency Department Encounters for Vomiting After Cannabis Legalization in Colorado



Cannabis hyperemesis syndrome is an emerging clinical issue associated with cannabis use. Legalization of cannabis has led to an increase in vomiting-related illnesses in health care settings.


To examine whether legalization of cannabis in Colorado has been associated with increases in vomiting-related emergency department (ED) visits.

Design, Setting, and Participants  

A cross-sectional design was used to assess the increase in ED claims for vomiting reported to the Colorado Hospital Association between January 1, 2013, and December 31, 2018, in counties that had no prior cannabis dispensaries before legalization compared with those that did. A total of 820 778 patients seeking care through Colorado EDs were included in the analysis.


The number of medical and recreational cannabis dispensaries per county per quarter.

Main Outcomes and Measures  

County per capita rate of vomiting-related ED claims per quarter.


Vomiting-related ED health care encounters increased from 119 312 in 2013 to 153 699 in 2018 (29% increase). Over this period, 203 861 patients (25%) were aged 0 to 18 years; 114 201 (14%) were aged 19 to 25 years, and 502 771 (61%) were aged 26 years or older; 510 584 patients (62%) were female. Additional recreational dispensaries were associated with increased vomiting-related ED visits (incidence rate ratio, 1.03; 95% CI, 1.01-1.05), but counties with high baseline medical dispensary exposure experienced smaller increases in vomiting-related ED visits than counties with no baseline medical dispensary exposure (incidence rate ratio, 0.97; 95% CI, 0.95-0.99). Counties with a high number of medical marijuana dispensaries had increases at a 5.8% slower rate than counties with none.

Conclusions and Relevance  

The findings of this study suggest that cannabis legalization in Colorado is associated with an increase in annual vomiting-related health care encounters with regard to exposure to these markets. It may be useful for health care clinicians to be aware of cannabis hyperemesis syndrome and inquire about cannabis use when appropriate.

The full study is available in JAMA Network Open.