A new study suggests that anyone who smokes marijuana faces a threefold risk of dying from high blood pressure than people who have never used the drug.
Those findings sound alarming, but it's important to keep in mind that, like any study, this one has limitations, including that it defines marijuana "users" as anyone who's ever tried the drug and that it doesn't differentiate among strains of a highly unregulated product.
However, the study highlights some key areas for future study - including how using cannabis might affect the heart. Here's what you need to know.
'A greater than three-fold risk of death'
"We found that marijuana users had a greater than three-fold risk of death from hypertension and the risk increased with each additional year of use," Barbara Yankey, the lead author of the study and a doctoral student of epidemiology and biostatistics at Georgia State University, said in a statement.
For her paper, published Wednesday in the European Journal of Preventive Cardiology, Yankey looked at more than 1,200 people age 20 or older who had been recruited previously as part of a large and ongoing national health survey.
In 2005, researchers asked them whether they had ever used marijuana or hashish. People who answered "yes" were classified as marijuana users; those who answered "no" were classified as nonusers.
The researchers then merged that data with statistics on death from all causes, pulled from the US National Center for Health Statistics, and adjusted it to rule out any factors that could muddle the results, like gender, race, and a history of smoking tobacco.
Overall, those classified as marijuana users were found to be 3.42 times as likely to die from hypertension, or high blood pressure, than those who said they had never used. That risk also appeared to rise by a factor of 1.04 with what the researchers labeled "each year of use."
Here's the problem: The study's authors defined anyone who said they had ever tried marijuana as a "regular user."
Other research suggests this is a poor assumption. According to a recent survey, about 52% of Americans have tried cannabis at some point, yet only 14% said they used the drug "regularly," defined as "at least once a month."
Also, the study was observational, meaning it followed a group of people over time and reported what happened to them, so the researchers cannot conclude a cause and effect - they can't say that smoking marijuana causes high blood pressure, only that the two things appear to be linked. The authors wrote, "From our results, marijuana use may increase the risk for hypertension mortality."
Another issue is the unregulated nature of the existing, and largely illegal, cannabis market. People are using a wide variety of strains whose concentrations of compounds - there are up to 400 in marijuana, including THC and CBD - can differ drastically.
Charles Pollack, who directs the Lambert Center for the Study of Medicinal Cannabis and was not involved with the new study, told LiveScience that there were many strains of marijuana "with no quality standards," and that was "making it tough to generalize" the effects.
Marijuana and your heart
While the study is far from conclusive, it sheds light on an important potential health risk linked with marijuana use. Scientists know that cannabis affects the heart, but because of the limited research available on the drug, it has been hard to suss out how it affects things like high blood pressure.
For example, according to the National Institute on Drug Abuse, ingesting marijuana increases heart rate by between 20 and 50 beats a minute for anywhere from 20 minutes to three hours.
But a large, recent report from the National Academies of Sciences, Engineering, and Medicine found "insufficient evidence" to support or refute the idea that cannabis might increase the overall risk of a heart attack, though it also found some limited evidence that using the drug could be a trigger for the phenomenon.
When it comes to cannabis' effect on blood pressure, the results are also inconclusive. One very small study, for example, found a sharp increase in blood pressure immediately after regular pot users stopped using the drug.
"Abrupt cessation of heavy cannabis use may cause clinically significant increases in blood pressure in a subset of users," that study's researchers wrote.
And according to the Mayo Clinic, using cannabis could result in decreased, not increased blood pressure.
Francesca Filbey, the director of cognitive neuroscience research of addictive disorders at the Center for BrainHealth and an associate professor in the School of Behavioral and Brain Sciences, told Business Insider that the latest study is an important area for future research, and said the links the study authors found "between death from hypertension and years of marijuana use does indicate a relationship" between the two things.
Still, Filbey said the study has important limitations, and said future studies should aim to also look at how factors like other substance use, BMI and other factors that may affect heart health could play a role in the outcome as well.
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