One of the difficulties in studying the epidemiological link between marijuana use and disease is the fact that most people who smoke marijuana also smoke cigarettes, making it hard to pry the effects apart in a statistical analysis. Siddarth Shah and colleagues just published an important analysis that avoids this problem by only studying never smokers. Their paper, “Association of Marijuana Use and Cardiovascular Disease: A Behavioral Risk Factor Surveillance System Data Analysis of 133,706 US Adults,” published in American Journal of Medicine used data from the 2016, 2017 and 2018 CDC national Behavioral Risk Factor Surveillance System (BRFSS) to measure the association between marijuana use and heart disease and stroke risk.
They found that never tobacco smokers who smoked marijuana 10 or more days a month the risk of having a heart attack or coronary artery disease and stroke were nearly doubled (OR 1.88, 95% CI 1.15-3.08 and OR 1.81, 95% CI 1.14-2.89, respectively) among adults 18-74. As with cigarette smoking, the risks were even higher for younger adults (men under 55 women under 65).
These risks overlap the low end of risks observed among cigarette smokers, probably because people who smoke marijuana do not smoke as heavily as people who smoke cigarettes.
Risks were not significantly increased for people who smoked marijuana less than 10 days a month or who used non-smoked forms.
Moving beyond epidemiology, it is important to understand that these increased risks are risks exactly what one would expect based on the fact that marijuana inhalation has immediate adverse effects on blood vessels (see, for example, this paper).
These finding should be of particular concern to people who are smoking “medical” marijuana because of the side effect of increased risk of heart attack or stroke when there was a safer alternative (non-smoked form) is available.
This finding is also relevant to the current debate over a proposed smokefree multi-unit housing ordinance in San Francisco (and likely elsewhere) which currently has an exemption for smoking medical marijuana even though the marijuana smoke, like tobacco smoke, migrates to the rest of the building, exposing nonsmokers. Smoked marijuana should not be exempt; there are other forms that provide the drugs without the pollution … and are probably safer for the person using the marijuana.
Here is the abstract from the paper:
Aim: Marijuana is the most commonly used psychoactive drug, while its effects on cardiovascular health are not well known and remain a subject of interest.
Methods: We used the pooled 2016 – 2018 data from the Behavioral Risk Factor Surveillance System (BRFSS) to perform a cross-sectional analysis evaluating the association of marijuana and cardiovascular disease, among US adults who never smoked cigarettes.
Results: Among US adults aged 18-74 years, when compared to non-users, frequent marijuana use was associated with 88% higher odds of myocardial infarction or coronary artery disease [adjusted odds ratio (aOR) 1.88, 95% confidence interval (CI) 1.15-3.08], and 81% higher odds of stroke (aOR 1.81, 95% CI 1.14-2.89). Among the premature cardiovascular disease group, frequent marijuana users had 2.3 times higher odds of myocardial infarction or coronary artery disease (aOR 2.27, 95% CI 1.20-4.30), and 1.9 times higher odds of stroke (aOR 1.92, 95% CI 1.07-3.43). In terms of the modality of marijuana use, frequent marijuana smoking had 2.1 times higher odds of myocardial infarction or coronary artery disease (aOR 2.07, 95% CI 1.21-3.56), and 1.8 times higher odds of stroke (aOR 1.84, 95% CI 1.09-3.10). A similar association was observed in the premature cardiovascular disease group who smoked marijuana [aOR (for myocardial infarction or coronary artery disease) 2.64, 95% CI 1.37-5.09; aOR (for stroke) 2.00, 95% CI 1.05-3.79)]. No association was observed between marijuana use in any form other than smoking and cardiovascular disease, across all age groups.
Conclusion: Frequent marijuana smoking is associated with significantly higher odds of stroke and myocardial infarction or coronary artery disease, with a possible role in premature cardiovascular disease.
The full citation for the paper is: Shah S, Patel S, Paulraj S, Chaudhuri D. Association of Marijuana Use and Cardiovascular Disease: A Behavioral Risk Factor Surveillance System Data Analysis of 133,706 US Adults. Am J Med. 2020 Nov 9:S0002-9343(20)30959-1. doi: 10.1016/j.amjmed.2020.10.019. Epub ahead of print. PMID: 33181103. It is available here.