Nearly half the country has legalized recreational cannabis, and at least a few more states may consider it in the near future. But as enjoyable as cannabis may be for many, research today may point to a possible downside of the drug: a higher risk of cardiovascular problems.
Boston researchers studied hospitalization rates in parts of the country that legalized cannabis earlier than others. Compared to the pre-legalization era and non- adopters, rates of several cardiovascular problems, including heart attacks, increased in the western half of the United States that was the first to adopt recreational cannabis, they found. Although this study is not definitive proof that cannabis can cause heart problems, it is the first study to explicitly link the expansion of legal cannabis to such problems, the researchers say.
“Our results highlight the potential harmful effects of recreational legalization on population health,” the authors wrote in their study published today in the journal BMJ Open.
An experiment on natural cannabis
Numerous studies and case reports in recent years have linked cannabis use to a higher risk of cardiovascular disease. Yet other studies have failed to find any link, and some have even suggested that certain cannabis ingredients, like cannabidiol, may actually lower blood pressure.
Studying the possible health effects of cannabis through the lens of legalization may offer some advantages over studies looking at cannabis use at the individual level, researchers say. People who use cannabis may differ in other important, less visible ways that could affect their risk of developing certain health problems compared to people who don’t use cannabis, for example. The history of recreational legalization in the United States also created a sort of natural experiment for researchers to study.
In 2014, Colorado became the first U.S. state to legalize cannabis, following the passage of a ballot initiative in 2012. Over the next few years, many western U.S. states quickly followed suit. In 2018, most people in the region lived in or next to a state that legally sold cannabis. However, it wasn’t until late 2018 that Massachusetts became the first eastern state to open legal dispensaries. Given this trend, researchers could examine what happened to early adopters after legalization.
The team analyzed data from the National Inpatient Sample, the largest publicly available database of hospitalized patients collected from medical centers across the country.
They specifically looked at hospital diagnoses related to cardiovascular disease from 2012 to 2018, with a particular focus on the Western U.S. Census Region, which includes the states of Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. They compared hospitalization rates in this region before and after legalization began to take hold in 2014; they also compared rates between the West and other regions of the United States during this study period.
Before legalization, hospitalization rates in the Western United States were generally lower than the rest of the country, but they began to increase more quickly after 2014. After adjusting for possible factors, the team found a statistically significant link between cannabis legalization in the West and increased rates of three cardiovascular conditions. For every year of legal cannabis use, rates of atrial fibrillation (irregular heartbeat), heart failure and heart attacks increased by about 2%, almost 4% and about 3%, respectively, they calculated.
What should this mean for cannabis and the heart?
This research is still observational, meaning it can only demonstrate a correlation between cannabis legalization and increased hospital visits for cardiovascular disease, not a clear cause-and-effect relationship. The data used in the study is also not specific enough to compare individual states to each other.
That said, the researchers conducted further analyzes to strengthen their findings. They found that cannabis-related diagnoses also increased in the western United States after legalization, while rates of urinary stones – a condition likely unrelated to cannabis – remained stable. This suggests that legalization has actually contributed to an increase in cannabis-related health problems at the population level, some of which may involve our cardiovascular system.
The authors are certainly not calling for cannabis to be banned. At the same time, they say their findings support “a cautious approach” to future legalization — one that would allow for detailed data collection on cardiovascular outcomes in places that embrace recreational weed. They also argue that their findings support ongoing efforts to reclassify cannabis from a Schedule I controlled substance in the United States to a Schedule III drug.
Importantly, a Schedule III classification would make it easier for scientists to study cannabis and its health effects in the laboratory (in April, the federal government reclassified medical cannabis to Schedule III, although it is still evaluating a decision on recreational cannabis). And this type of research would help answer relevant questions, such as identifying the exact components of cannabis that might increase heart risk in people, whether there is a threshold effect (daily or occasional use), or whether the route of administration is important (for example, smoking it versus edibles).
Recreational cannabis is here to stay, but we need to learn more about how it can influence our health, both good and bad.
Gn Health
