The results of a recently published study reveal what the authors describe as the “cannabis paradox”: Despite fears that marijuana use may be linked to some heart problems, adults hospitalized after a heart attack actually seemed to fare better when they used cannabis.
“The results of our study reveal a paradox,” the researchers wrote. “Among patients aged 18 to 80 years hospitalized with (acute myocardial infarction) in the United States between 2001 and 2020, cannabis use was associated with a lower risk of complications such as cardiogenic shock, acute ischemic stroke, cardiac arrest, and (percutaneous coronary intervention), as well as lower in-hospital mortality, even after adjusting for several confounding factors.”
“This underscores that despite a steady increase in its use and social acceptance, cannabis remains a poorly understood substance,” they added.
The report, published in the journal Archives of Medical Science – Atherosclerotic Diseases, examined data from the National Nationwide Inpatient Sample, a database of hospital discharge records across the United States that, according to the authors, “represents more than 97% of the U.S. population.”
“Cannabis users were less likely to experience all-cause hospital mortality when admitted for an acute myocardial infarction.”
One reason the 10-person research team – which included members from the US, UK and Mauritius – found the results so surprising is that some scientific evidence suggests a negative link between marijuana and heart health.
“Epidemiological studies have demonstrated an association between cannabis use and an increased risk of developing coronary heart disease,” the study states. “However, studies on the influence of cannabis use on the consequences of acute myocardial infarction (AMI) are lacking.”
The authors said their study appears to be “the first to conduct an in-depth investigation of the association between cannabis use and hospital outcomes using a representative sample of the U.S. population admitted for acute myocardial infarction over a two-decade period.”
“The most surprising finding of our study is that cannabis use is associated with lower in-hospital mortality after acute myocardial infarction,” they wrote. In particular, marijuana users “had lower odds of overall in-hospital mortality when admitted for acute myocardial infarction.”
The researchers cited several factors to explain the “cannabis paradox.” First, they noted that the cannabis users in the study were generally younger than the non-users – an average of 51.0 years versus 62.7 years. “This age difference may be the reason for the lower prevalence of known cardiovascular risk factors that are generally associated with increasing age,” the study states, “such as hypertension, dyslipidemia, diabetes, chronic kidney disease, previous CABG, and peripheral vascular disease.”
Nevertheless, “even after propecticity matching and accounting for these potential confounders, cannabis use continued to be associated with a survival benefit in AMI,” according to the team’s analysis.
Another possibility is that cannabinoids themselves provide some benefit for heart health, or, as the researchers put it, “provide cardiac protection modulated by cannabinoid receptor type 2 activation,” based on some evidence of protective benefits in studies of mouse models.
“Given that the complex mechanisms by which cannabis achieves immune modulation remain to be fully investigated and understood,” they wrote, “hopefully the results of studies similar to ours will provide the necessary impetus to advance research in this area even further.”
Another possibility is that the causes of heart attacks among cannabis users are different from those of non-users, as the study explains:
“The primary mechanism of AMI in cannabis users may differ from the most commonly observed etiology of atherosclerotic plaque destruction causing acute thrombosis. Studies have shown that cannabis upregulates the sympathetic portion of the autonomic nervous system while inhibiting the parasympathetic portion, resulting in an increase in heart rate, an increase in blood pressure, and a reduction in coronary blood flow. These changes may also trigger certain arrhythmias, such as: B. supraventricular tachycardia and ventricular tachycardia, which were more common in cannabis users in the present study, whereas the higher predisposition to atrial fibrillation and ventricular fibrillation in our cohort of non-cannabis users could be explained by age-related structural and functional remodeling specific to these arrhythmias… Our observation that cannabis users underwent PCI less frequently compared with non-users suggests that they are less likely to have obstructive coronary artery disease as the underlying cause of their AMI.”
The authors said the study had some limitations. For example, it could be affected by underreporting of cannabis use or by documentation errors at the hospital level. They also said it was possible there were confounding variables that were not identified or adjusted for in their analyses.
“Finally, we cannot determine the relationship between timing or amount of cannabis use and acute myocardial infarction,” they wrote. “We cannot adjust for past rather than regular or recent cannabis use, which is theoretically less likely to lead to acute myocardial infarction or to affect outcomes after acute myocardial infarction.”
The researchers also found that the “cannabis paradox” has parallels to earlier findings on tobacco use, which had led to the term “smoker’s paradox.”
“The beneficial effect of cannabis use on short-term outcomes after AMI reflects the ‘smoker’s paradox,'” the report states, “where a similar short-term survival benefit was observed in tobacco smokers after treatment for AMI, regardless of whether they underwent thrombolysis or percutaneous coronary intervention.”
The study follows another study showing that medical marijuana use in older adults may have several therapeutic benefits for this population, including health, well-being, sleep and mood. The authors also observed “significant reductions in pain intensity and pain interference in older patients who report chronic pain as a primary condition.”
The study, published in the journal Drugs and Aging, aims to address what the authors describe as “a general lack of high-quality research” on cannabis and older adults, “as well as a common methodological practice of excluding people over 65 years of age from clinical trials,” at a time when older patients are increasingly turning to medical marijuana to relieve their symptoms.
Meanwhile, a government-funded study conducted last year found that both cannabis and psychedelic use among U.S. adults had reached “historic highs,” while marijuana use among teenagers had remained stable.
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Photo courtesy of Mike Latimer.
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