Almost half of the United States has legalized recreational cannabis, with more states expected to consider it soon. While many enjoy cannabis, recent research suggests a possible downside: an increased risk of cardiovascular issues.
Researchers in Boston examined hospitalization rates in areas that legalized cannabis earlier than others. Their findings revealed that rates of various cardiovascular events, including heart attacks, increased in the western U.S., where recreational cannabis was first legalized. Although this study doesn’t definitively prove that cannabis causes heart issues, it is the first to link the legal expansion of cannabis to these health concerns.
“Our findings indicate potential negative effects of recreational cannabis legalization on public health,” the authors noted in their study published today in BMJ Open.
A natural experiment with cannabis
Several studies and case reports over recent years have connected cannabis use with a heightened risk of cardiovascular diseases. However, some research has not found any link, and there are instances where ingredients like cannabidiol are believed to lower blood pressure.
The researchers highlight that studying the health impacts of cannabis through the lens of legalization can provide unique insights compared to analyzing individual cannabis users. Individuals who use cannabis may have different backgrounds that could influence their health compared to non-users. The history of cannabis legalization in the U.S. also serves as a sort of natural experiment for this research.
In 2014, Colorado was the first state to legalize cannabis, prompted by a ballot initiative in 2012. Over the next few years, many western states followed suit. By 2018, most residents in that region were either living in or near states with legal cannabis. It wasn’t until late 2018 that Massachusetts became the first state on the east coast to open legal dispensaries, allowing researchers to analyze the outcomes for early adopters post-legalization.
The research team utilized data from the National Inpatient Sample, which is the largest publicly available database of hospitalized patients gathered from medical facilities across the U.S. They focused specifically on hospital diagnoses related to cardiovascular diseases from 2012 to 2018, particularly in the western U.S., which includes states like California, Colorado, and Washington. The researchers compared hospitalization rates before and after legalization began in 2014 and also looked at trends across different regions of the country.
Before legalization, hospitalization rates in the western U.S. were generally lower than in other parts of the country, but they began to rise more sharply after 2014. After accounting for various factors, the researchers found a statistically significant connection between cannabis legalization in the West and increasing rates of three cardiovascular-related outcomes. For each year of legalized cannabis, the rates of atrial fibrillation, heart failure, and heart attacks climbed by approximately 2%, almost 4%, and around 3%, respectively.
Implications for cannabis and cardiovascular health
This research is observational, indicating it can show a correlation between cannabis legalization and rising hospital visits for cardiovascular issues, but not establish a clear cause-and-effect relationship. Additionally, the data do not allow for state-by-state comparisons.
That said, the researchers conducted further analysis to support their findings. They noticed that cannabis-related diagnoses also rose in the western U.S. after legalization, while rates of urinary stones, a condition likely unrelated to cannabis, remained stable. This suggests that legalization likely led to an increase in cannabis-related health issues on a population level, some of which could involve cardiovascular health.
The authors are not calling for cannabis to be banned. However, they do advocate for a “cautious approach” to future legalization—one that includes detailed data collection on cardiovascular outcomes in regions that legalize recreational cannabis. They also propose reclassifying cannabis from a Schedule I controlled substance to a Schedule III drug in the U.S.
A Schedule III classification would facilitate research on cannabis and its health effects in laboratories. Recently, the federal government reclassified medical cannabis as Schedule III, although it is still evaluating recreational cannabis. This kind of research would help clarify important questions, like identifying cannabis components that might elevate heart risk, determining if there’s a threshold effect based on frequency of use, or whether the method of consumption—like smoking versus edibles—makes a difference.
Recreational cannabis seems here to stay, but understanding its impacts on health, both positive and negative, is crucial.
