Of 453 potential marijuana-related ER visits flagged by surveillance queries in Colorado, 188 (45%) were confirmed as true cases, with edible users and out-of-state visitors disproportionately affected.
Public health officials, ER physicians, and policymakers evaluating legalization outcomes.
Edibles & tourists overrepresented
What the researchers found
Of 44,942 total ER visits, 1% were flagged as potential marijuana cases; 188 of 422 reviewed records (45%) were confirmed acute adverse effects. 95% reported intentional use. Non-Colorado residents and edible users were significantly overrepresented among confirmed cases compared to non-cases.
Why it matters
Post-legalization monitoring requires validated surveillance tools. This study confirms that existing ER data systems can reliably track marijuana-related visits, enabling evidence-based policy responses.
The numbers in context
44,942 total ER visits; 453 flagged (1%); 188 confirmed cases; 58% male; 95% intentional use; PPV ranged 36-64% by hospital; edible users and non-residents significantly overrepresented.
How the study worked
Validation study comparing syndromic surveillance queries (ICD-10 codes and keywords) against physician-reviewed medical records at 3 Colorado hospitals during 2016-2017.
What this study cannot tell us
Three hospitals in one Colorado county, not statewide. PPV varied substantially by hospital. Only captures ER presentations, missing less severe adverse effects managed at home or in urgent care.
How to read the evidence
Moderate: validated surveillance methodology with physician chart review, but limited to three hospitals.
When this study was published
Published in 2019.
The bigger picture
The overrepresentation of tourists and edible users among confirmed cases aligns with concerns about inexperienced consumers encountering legal cannabis. Surveillance data like this can guide targeted public health messaging.
Questions still open
- Have marijuana-related ER visits continued to rise since 2017? Would standardized patient intake questions about cannabis use improve surveillance accuracy?
Common questions
How common are marijuana ER visits in Colorado?
Who is most likely to end up in the ER from marijuana?
Read the original research
Syndromic Surveillance of Emergency Department Visits for Acute Adverse Effects of Marijuana, Tri-County Health Department, Colorado, 2016-2017.
Public health reports (Washington, D.C. : 1974), 134(2), 132-140
Citation
Marx, Grace E; Chen, Yushiuan; Askenazi, Michele; Albanese, Bernadette A. (2019). Syndromic Surveillance of Emergency Department Visits for Acute Adverse Effects of Marijuana, Tri-County Health Department, Colorado, 2016-2017.. Public health reports (Washington, D.C. : 1974), 134(2), 132-140. https://doi.org/10.1177/0033354919826562
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