In Colorado, marijuana-related hospitalizations doubled (274 to 593 per 100,000), ER visits with marijuana codes had 5x more mental illness, and poison control calls nearly doubled again after recreational legalization in 2014.
Readers interested in the health system impact of cannabis legalization.
Marijuana-related hospitalizations: 274 to 593 per 100,000. Poison control calls: +79.7% after recreational legalization
What the researchers found
Analyzing Colorado health data from 2000-2015, the study documented escalating marijuana-related healthcare contacts across three measures.
Hospitalizations with marijuana-related billing codes increased from 274 per 100,000 in 2000 to 593 per 100,000 in 2015, more than doubling over the period. The increase accelerated after both medical (2010) and recreational (2014) liberalization.
Among ER visits with marijuana-related codes, the prevalence of mental illness was five-fold higher (5.07) than ER visits without marijuana codes, suggesting a strong association between marijuana-related emergencies and psychiatric conditions.
Poison control calls remained stable from 2000-2009, then significantly increased from 42 to 93 after medical marijuana policy liberalization in 2010. After recreational legalization in 2014, calls increased another 79.7% (from 123 to 221). Calls involving children under 17 also increased after 2014.
Why it matters
Colorado is the most-studied natural experiment in cannabis legalization. These data provide concrete evidence that legalization is associated with increased marijuana-related healthcare utilization. The five-fold higher rate of mental illness among marijuana ER visits is particularly important for understanding the psychiatric dimensions of cannabis use.
The numbers in context
Hospitalizations: 274 to 593 per 100,000 (2000-2015). Mental illness prevalence in marijuana ER visits: 5.07x higher than non-marijuana visits. Poison control calls: 42 (2009) to 93 (2010, post-medical), then 123 to 221 (2013-2014, post-recreational, +79.7%). Under-17 calls also increased after 2014.
How the study worked
Retrospective analysis using Colorado Hospital Association data (hospitalizations and ER visits with marijuana billing codes), and Regional Poison Center marijuana exposure calls, from 2000 to 2015.
What this study cannot tell us
Billing code-based analysis may capture marijuana mentions that are incidental rather than causal. Increased coding and disclosure after legalization may inflate the apparent increase. The study cannot determine what proportion of increased healthcare contacts represents genuinely new problems versus better detection. No comparison state data was included.
How to read the evidence
Strong evidence from comprehensive state-level healthcare data spanning 15 years.
When this study was published
Published in 2017, using data through 2015. Colorado's market has continued to evolve.
The bigger picture
These increases likely reflect multiple factors: true increases in marijuana use and related problems, increased willingness to disclose marijuana use when legal, better diagnostic coding, and greater availability of high-potency products. Disentangling these factors is critical for accurately assessing legalization's public health impact.
Questions still open
- How much of the increase reflects true new health problems versus better detection and reporting? Are specific products (edibles, concentrates) driving the increase? Has the rate of increase stabilized as the legal market has matured?
Common questions
Did legalization increase marijuana-related health problems in Colorado?
Why do marijuana-related ER visits have so much mental illness?
Read the original research
Marijuana and acute health care contacts in Colorado.
Preventive medicine, 104, 24-30
Citation
Wang, George Sam; Hall, Katelyn; Vigil, Daniel; Banerji, Shireen; Monte, Andrew; VanDyke, Mike. (2017). Marijuana and acute health care contacts in Colorado.. Preventive medicine, 104, 24-30. https://doi.org/10.1016/j.ypmed.2017.03.022