A new study, heavily hyped in mainstream media, claims that cannabis poses greater risks than tobacco to cardiovascular health, particularly with hypertension. But the key word is “hype,” because the study’s methods don’t really support that conclusion.
Authors of the research used a “retrospective study” design. That is to say, they didn’t identify any new cannabis consumers to compare their health to that of non-users. Instead, subjects who had previously acknowledged ever having used cannabis in a 2005-2006 nutritional study, the National Health and Nutrition Examination Survey, were used.
Participants who admitted having engaged in past cannabis use were then automatically classified by the study’s scientists as “current users” of weed. No evidence exists to corroborate this claim.
An even greater problem is the fact that to calculate the estimated length of each subject’s cannabis use, scientists simply subtracted the age at which participants first reported trying weed form their current age. For example, if one reported having experimented with marijuana at age 20, and is now 40 years old, the study’s investigators classified this person as a “20-year marijuana user.”
Now, making the assumption that someone who has “ever used” cannabis will continue to use it unceasingly for the rest of his or her life is pretty silly While an estimated half of all adults admit having tried marijuana, typically during young adulthood, most do not continue consuming it long term, as noted by Gallup and others, particularly after age 30. (According to Gallup, only about one of every eight Americans defines themselves as a “current user” of cannabis.)
The authors actually acknowledged this serious shortcoming in their press release: “[T]here were limitations to the way marijuana use was estimated,” they wrote.
For example, it cannot be certain that participants used marijuana continuously since they first tried it”), they opined that such unconventional methodology was necessary because there exists an “absence” of longitudinal data assessing the long-term use of cannabis and cardiovascular health.
Too bad the above assertion is false. Two longitudinal trials have been published in the past few months specifically addressing cannabis use and heart health.
Cardiovascular cannabis studies are available
Data published last year in the Journal of the American Medical Association delved into the relationship between cannabis use over a 20-year period and overall health. The study examined 1,037 people.
We found no association between cannabis and cardiovascular risks [e.g., high blood pressure, higher cholesterol]. In general, our findings showed that cannabis use over 20 years was unrelated to health problems early in mid-life.
An international team of scientists wiring in the American Journal of Public Health looked at cannabis use and cardiovascular risk in a group of more than 5,000 individuals over a period of more than two decades.
Compared with no marijuana use, cumulative lifetime and recent marijuana use showed no association with incident CVD (cardiovascular disease), stroke or transient ischemic attacks, coronary heart disease, or CVD mortality.
These findings are similar to those of several other studies finding that exposure to cannabis doesn’t appear to be linked to significant cardiovascular risk in otherwise healthy people.
Tobacco’s a different story
Cigarette smoke, on the other hand, is a well-established contributor to bad cardiovascular outcomes. For example, smoking tobacco has been estimated to increase the risk of strokes by up to 600 percent.
While it’s well established that cannabis can affect blood pressure, tolerance to these effects seems to develop quickly.
Sensational claims that cannabis is a greater risk to heart health that tobacco are simply not based on any verifiable evidence, and shouldn’t be taken seriously at this time, according to Paul Armentano of NORML.