Colorado Experiences Rise in Cases of Cyclic Vomiting Syndrome Following Cannabis Legalization

Colorado is home to one of the longest established cannabis industries in the United States, having introduced some rudimentary medicinal cannabis legislation as early as 2000, and becoming the first state to fully cease cannabis prohibition in 2012. As a result, Colorado has become an important state for cannabis research due to the wealth of data available for researchers to review and analyze.

One such review has recently been electronically published ahead of print in the Internal Medicine Journal. The review, led by Dr. Sanjay Bhandari, Assistant Professor at the Medical College of Wisconsin, analyzes all hospital admissions in Colorado between the years of 2010 and 2014 in order to establish whether recent trends in hospital admissions for cases of cyclic vomiting syndrome may be linked to variations in cannabis use during the same timeframe.

What is cyclic vomiting syndrome?

Cyclic Vomiting Syndrome, or CVS, is a functional gastrointestinal disorder that causes prolonged episodes of severe nausea and vomiting. These episodes can last from a few hours to several days; often happening unpredictably with weeks or even months between episodes. In many cases, episodes can be so severe that it is necessary for people with CVS to seek treatment at an emergency room or be admitted to hospital until symptoms ease.

As well as nausea and frequent vomiting, people having a CVS episode may also experience other symptoms such as slight abdominal pain, fever, headaches, dizziness, and the development of a sensitivity to bright lights or loud sounds. While CVS itself is not particularly dangerous, it can cause serious complications such as dehydration or esophagitis if those affected are not given proper care or aftercare following episodes.

Episodes of CVS can sometimes be triggered by external factors, such as physical exhaustion, sleep deprivation, hot weather, or certain food triggers. Additionally, CVS is also thought to be linked to migraine, as many CVS sufferers also go on to develop migraines, and migraine medicines have shown some effectiveness towards treating episodes of CVS.

As well as the suspected migraine link, CVS is also thought to be linked to patient history of long-term cannabis use.

Analysis of CVS cases in Colorado

The recent review of CVS cases in Colorado looked at all hospital admissions in the state of Colorado between 2010-2014, of which there were 4,715 CVS-related hospitalizations, and 2,359,247 non-CVS related hospitalizations. 1,823 of the CVS hospitalizations listed CVS as the primary diagnosis. When CVS was not the primary diagnosis, patients were most often admitted for acute kidney injury or dehydration. When CVS was the primary diagnosis, both dehydration and kidney injuries were common secondary diagnoses, along with hypopotassemia.

It was found that there was a significant increase in all CVS cases between 2010 and 2014, rising from 806 in 2010, to 1180 in 2014 - an increase of 46%. Measuring just from 2012, the year when recreational cannabis use was legalized, there was an increase of 32% in all CVS cases. In cases where CVS was the primary diagnosis, there was no similar increase observed.

By looking at patient medical history, it was also possible to establish the prevalence of cannabis use in patients hospitalized with CVS versus non-CVS diagnoses. Both patient groups saw an abrupt increase in reported cannabis use following recreational legalization in 2012, but overall, patients with a diagnosis of CVS were significantly more likely to report cannabis use. Specifically, the average cannabis use prevalence for non-CVS patients was 1.7%, compared to 13% in all CVS diagnoses and 17% when CVS was listed as the primary diagnosis.

Multivariate logistic regression analysis was also used in the course of the review to determine any predictors of cannabis use in CVS. The resultant predictors included: being of young age (18-45 years), male, African-American, uninsured, or having Medicare. The reasons why these demographics might be more likely to experience cannabis use in CVS is unclear, though the reviewers do note that it has been previously shown that young males are the most likely user group in the general population.

Conclusions of the study

The review shows a strong correlation between increasing numbers of CVS cases and the steps made in cannabis legalization in the same timeframe. The reviewers posit that this could be due to an increased awareness of CVS following legalization, or a true increase in CVS cases caused by increased cannabis consumption, or even possibly a combination of the two. Similarly, the increased prevalence of reported cannabis use in CVS and non-CVS patients could be down to patients feeling more comfortable in disclosing cannabis use now that it is legal, a true increase in cannabis usage statistics, or a combination.

Identifying whether this increase is artificial or real is near-impossible to achieve from a database analysis such as this. However, further medical and clinical study of the mechanism through which CVS operates, or other links between cannabis use and nausea, could conclusively show the extent to which cannabis use influences the development of the syndrome.

A further limitation identified by the researchers is the existence of other syndromes with similar symptomatic profiles. For example, there have been several case reports of a condition known as Cannabinoid Hyperemesis Syndrome, or CHS, which exhibits similar episodes of nausea and vomiting to CVS. CHS is also characterized by chronic cannabis use and the learned behavior of frequent hot bathing, which sufferers report can temporarily ease symptoms. As the mechanism behind CHS remains unknown, it is often extremely difficult to differentiate between cases of CVS and CHS. Some researchers have suggested that the only major difference between both conditions is whether vomiting episodes stop occurring once cannabis consumption is ceased, but knowing this requires a long-term follow-up on the patient, which is rare. As a result, case reports of CVS may be inflated or underreported due to misdiagnosis.

Despite the limitations of this study, it still provides a wealth of valuable information describing the trends observed so far in CVS diagnoses, particularly with respect to cannabis use as a potential predictor or trigger of CVS. The correlation in CVS cases and cannabis use certainly indicates that further clinical research on the topic is warranted, especially as a growing number of states and countries anticipating legalizing cannabis use may soon find themselves affected by similar patterns.