The pros and cons of marijuana usage are complicated, and are constantly being updated as new research emerges and the drug gains popularity thanks to decriminalization legislation. Unfortunately for fans of the drug, a new study led by researchers at Stanford University has dropped a big weight on the "cons" side of the scale: daily marijuana use has been associated with a 34% increase in coronary artery disease compared to those who have never taken the drug.
As marijuana use becomes more acceptable, researchers are scrambling to understand just how the various compounds in the cannabis plant impact those who use it. In terms of the negative impacts, in recent years we've seen a study linking the heavy metals in the plants to the potential to develop chronic diseases like Alzheimer's; another showing that it is associated with more rebound headaches in migraine sufferers; and still another demonstrating that super-potent strains of marijuana can lead to higher incidences of psychotic disorders.
In the positive column, cannabis has shown the ability to cut seizures in epileptic children by a whopping 86%; reduce the gut inflammation associated with inflammatory bowel disease; improve insomnia; and reduce OCD symptoms.
This latest study on marijuana's health effects by the Stanford researchers makes a compelling case in the cons column, showing that daily users of the drug are about one third more likely to develop coronary artery disease (CAD) than those who've never tried it. CAD is marked by plaque buildup on the walls of the arteries that supply the heart with blood.
The study used the All of Us Research Program as its dataset. The program is an effort by the National Institutes of Health to gather lifestyle and health data from one million people in the United States, to help accelerate research studies. When the Stanford scientists conducted their study, the system had detailed information from 175,000 people.
The researchers used self-reported data to determine marijuana usage and compared that with rates of diagnosed CAD. Because in studies like these it's notoriously tricky to tease out cause-and-effect relationships, the researchers not only applied adjustments for age, sex, and major risk factors for cardiovascular disease, they also used a technique known as Mendelian randomization.
This approach looks at genetic markers for behaviors to form causal relationships. In this case, the team looked at genetic markers that lead to cannabis use disorder – a psychiatric condition leading to frequent cannabis use and dependency – and CAD. The following video helps explain Mendelian randomization in more detail.
After applying these filters, the researchers reached their conclusions about the cardiovascular harms of daily marijuana usage.
"We found that cannabis use is linked to CAD, and there seems to be a dose-response relationship in that more frequent cannabis use is associated with a higher risk of CAD," said Ishan Paranjpe, MD, a resident physician at Stanford and the study’s lead author. "In terms of the public health message, it shows that there are probably certain harms of cannabis use that weren’t recognized before, and people should take that into account." The researchers also say cannabis users should be honest with their doctors regarding their intake of the drug so that health care practitioners can keep an eye out for potential complications.
THC and inflammation
The new research ties into the findings of a 2022 study, also led by researchers at Stanford, which found that THC caused inflammation in endothelial cells in the lab. These are the cells that line our blood vessels, and when they become inflamed, our risk of heart attack spikes.
"Marijuana has a significantly adverse effect on the cardiovascular system," said Mark Chandy, co-lead author on that study at the time. "As more states legalize marijuana use, I expect we will begin to see a rise in heart attacks and strokes in the coming years. Our studies of human cells and mice clearly outline how THC exposure initiates a damaging molecular cascade in the blood vessels. It’s not a benign drug."
Now that the link between marijuana use and heart disease has been strengthened, the current researchers feel that the findings could help them better understand and treat cardiovascular issues.
"From a scientific standpoint, these findings are exciting because they suggest there might be new drug targets and mechanisms we can explore to take control of this pathway going forward," Paranjpe said.
The study did not distinguish between marijuana intake methods, such as when it is smoked as a plant or consumed as some type of edible or tinctures, but the researchers believe teasing apart those distinctions might be a useful course of action for future efforts. There was no noticeable increase in CAD in users of the drug who partook only once per month.
The study will be presented at the 2023 American College of Cardiology meeting in New Orleans from March 4th to 6th.
Source: American College of Cardiology
