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Cannabis-related Vomiting is on the Rise in Colorado, Study Finds

By Alexander Beadle

Published: Sep 23, 2021   
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The number of vomiting-related emergency department visits in Colorado grew by nearly 30 percent after the state legalized recreational cannabis use, a new analysis has found.

Published in JAMA Network Open, the investigation found that the presence of recreational cannabis dispensaries in a county was associated with an increased number of vomiting-related emergency department (ED) visits at local hospitals. However, counties that already had a high number of medical dispensaries pre-recreational cannabis legalization experienced smaller increases in ED visits than those counties with no baseline exposure.

Given this increase and its association with exposure to cannabis markets, the researchers suggest that it might be helpful for healthcare providers in areas with legal cannabis access to familiarize themselves with cannabis hyperemesis syndrome (CHS) and inquire about cannabis use patterns with relevant patients where appropriate.

Legalization in Colorado linked to increase in annual vomiting-related incidents

Cannabis-related vomiting incidents and cases of CHS have previously been identified as an emerging clinical issue. The researchers behind this new JAMA Net. Open study set out to assess whether the legalization of recreational cannabis in Colorado in 2012 may have led to a subsequent increase in emergency department visits for repeated vomiting.

The researchers studied ED claims data from the Colorado Hospital Association for the period between January 1, 2013, and December 31, 2018, and identified all visits that were labeled with any diagnostic code for vomiting. These data were analyzed in combination with information on the number of licensed dispensaries present in each state county across the study timeframe, which was provided by the Colorado Department of Revenue Marijuana Enforcement Division.

At the state level, the researcher found that vomiting-related ED visits rose from 119,312 incidents in 2013 to 153,699 by 2018 – a 29 percent increase. The researchers also determined that the counties that had zero medical dispensaries before the opening of the recreational cannabis market saw the greatest increases in vomiting-related ED visits in both percentage and population-adjusted rates.

“These results suggest counties with no baseline exposure to medical cannabis markets experienced more vomiting-related health events with the new opening of recreational cannabis dispensaries than counties already introduced to these markets through medical dispensaries. This difference may be due to a lack of medical oversight regarding use in counties without a preexisting or coexisting medical market,” the researchers suggested.

Cannabis-related vomiting incidents may still be under-reported

The proportion of ED cases in Colorado that bore a cannabis-related International Classification of Diseases (ICD) diagnosis code also rose over the study period, from 0.3 percent in 2013 to 2.3 percent in 2018 – a seven-fold increase from baseline levels.

“These results also suggest that cannabis comorbidity is likely being underidentified in these vomiting cases,” the researchers wrote. “Although there was a 7-fold increase in the ICD coding of cannabis use with vomiting-related illness for health care encounters in Colorado, there were still too few to have a sufficiently powered analysis to examine them directly.”

Colorado is commonly known to have higher rates of cannabis use than the United States average, the researchers said, and so it would be surprising for there to be such a low percentage of cannabis involvement in ED visits if every case was being identified.

In light of these findings, the researchers recommend that healthcare professionals in states that have legal cannabis access become more familiar with the symptoms of cannabis hyperemesis syndrome and cannabis-related cycling vomiting episodes. Initiating conversations about cannabis use with these patients and being aware of potential treatment mechanisms is a crucial step in identifying these conditions and preventing complications and serious health risks.

What is cannabis hyperemesis syndrome?

CHS is predominantly characterized by repeated episodes of uncontrollable vomiting or nausea, often accompanied by abdominal pain or a loss of appetite, in people reporting frequent and heavy cannabis use.

Oddly, some long-term cannabis consumers with CHS report that these vomiting episodes can be temporarily relieved by taking hot baths or showers. This may devolve into developing problematic compulsive bathing behaviors, where these people spend hours or more in hot water at a time to try and find relief.

“They are writhing, holding their stomach, complaining of really bad abdominal pain and nausea,” first author Dr Sam Wang, a pediatric emergency medicine specialist and toxicologist at Children's Hospital Colorado, told CNN.

“They vomit and then just continue to vomit whatever they have in their stomach, which can go on for hours,” Wang continued. “They often say they took a scalding hot shower before they came to the ER but it didn’t help. That's when we know we may have a case of cannabis hyperemesis syndrome, or CHS.”

Where symptoms are extreme, people with CHS are at risk for developing severe dehydration, problematic weight loss, muscle spasms, seizures, and potentially fatal kidney failure if left untreated. Additionally, while cases of CHS might appear quite rarely in the medical literature, many believe that a significant number of CHS cases are being overlooked or misdiagnosed as cyclic vomiting syndrome (CVS), as both conditions have very similar indications if cannabis use is not properly considered.

Previous trials have suggested that long-term chronic use is one factor in developing CHS, but that it is perhaps not the whole story. The increasing potency of easily available high-THC cannabis products in recreational markets has also been floated as one possible explanation, for example.

“It’s been well documented that the amount of THC that now comes in cannabis is increasing substantially,” Wang commented. “In the ‘90s the average was like 4% or 5%. Now in Colorado, it’s anywhere from 15% to 20%.”

Although synthetic THC has been used clinically as an antiemetic in treating chemotherapy-related nausea, some theorize that this cyclic cannabis-related vomiting is due to a disequilibrium between the endocannabinoid system, brain stem, and hypothalamic-pituitary-adrenal axis, which reverses this effect after the heavy use of potent products.


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