Cannabis, Strokes, and Heart Attacks? 

The temporary quintupling of heart attack risk associated with cannabis smoking may be due to increased heart rate, blood pressure, and carbon monoxide levels.

Does “the dark side of cannabis”—both “synthetic and non-synthetic marijuana”—include stroke?

There have been case reports of artery damage due to the “vasoconstrictor effect of cannabis,” which has been well documented. One study found cannabis users had a hundred times greater odds of suffering from multifocal intracranial stenosis, where the arteries inside our brain clamp down at multiple points, as you can see below and at 0:39 in my video Does Marijuana Cause Strokes and Heart Attacks?, but that’s a rare condition. What about strokes? 

“The paucity [lack] of high-level evidence regarding the adverse effects of marijuana usage on cerebrovascular [brain artery] health has permitted the false notion that recreational marijuana is safe.” So, researchers decided to put it to the test in a study of millions of cannabis users and found that “recreational marijuana use is independently associated with 17% increased likelihood of AIS hospitalization,” that is, being hospitalized with an acute ischemic stroke, but that may only be among those who use cannabis regularly, “weekly or more often.”

The reason we think it’s cause-and-effect is that the majority of recorded strokes were “during or shortly after marijuana exposure,” and there are even cases in which strokes recurred after re-exposure to marijuana. So, when you put all of that together, it makes a convincing case. Though, to be sure, you’d need to randomize people to use cannabis or a placebo. 

It’s like the heart disease story. A similar “temporal” relationship has been found between marijuana use and the development of heart attacks and sudden cardiac death, meaning they seemed to occur while individuals were using cannabis or right after usage. “However, careful evaluation of the cardiovascular effects of marijuana inhalation is complicated by the fact that it is often used in combination with other drugs, such as alcohol or cocaine.” So, you can’t just ask heart attack victims if they were smoking pot at the time of a cardiac event and make the connection; you have to ask about other substance use, too. Within an hour of using cocaine, for example, the risk of having a heart attack goes up more than 20-fold.

That’s about four times more than after smoking pot. The hour after you smoke marijuana, your heart attack risk appears to nearly quintuple, but only for that hour. Then, your risk drops down to normal. So what does this mean? Even though heart disease is our number one killer, the risk of having a heart attack every hour is only about one in a million for any particular hour. So, even if you light up a joint, which may quintuple your risk, that would only bump up the risk to about 1 in 150,000 and only for that one hour. Even if you smoked every day, your annual risk might just go up by a few percentage points. But why the increased risk at all?

Well, we’ve known since the 1970s that within an hour of smoking a joint, our pulse rate goes up about 35 percent, as you can see below and at 3:20 in my video. Smoking a single joint also increases blood pressure, as well as carbon monoxide levels in the blood of angina patients, and it cuts their ability to exercise nearly in half. Now is that just because they’re breathing in smoke of any kind? No, smoking a placebo joint—that is, a marijuana joint from which the THC has been removed—only cuts down exercise capacity by about 9 percent. In contrast, after smoking an actual cannabis joint, the time the study participants could exercise before experiencing chest pain was cut by 48 percent. So, it does seem to be a specific drug effect. Is it as bad as tobacco? We found that out a year later. 

“Smoking 1 marihuana [sic] cigarette decreased the exercise time until angina more than smoking 1 high-nicotine [tobacco] cigarette,” which only cut exercise capacity by 23 percent, compared to 50 percent after the joint. This may be because smoking marijuana seems to put more demand on the heart, so it’s no surprise that it was worse than tobacco.

It may also be carbon monoxide. Smoking marijuana leads to nearly five times more carbon monoxide in the bloodstream than smoking tobacco. This is in part because, compared to cigarette smokers, cannabis smokers inhale more deeply and then hold in the smoke for longer, allowing more carbon monoxide into their system. So, the increased heart rate and pressure, the “cardio acceleration,” may account for the accelerated chest pain in heart disease patients.

Does cannabis have any chronic effects on the arteries? Users do seem to have relatively stiffer arteries for their age, suggesting “an acceleration of the aging process.” We are only as old as our arteries.

Even second-hand marijuana smoke may be harmful, according to a recent study in the Journal of the American Heart Association entitled, “One Minute of Marijuana Secondhand Smoke Impairs Vascular Endothelial Function,” meaning artery function. So, there was a call to protect “vulnerable populations, including elderly and disabled [multi-unit housing] MUH residents, pregnant women, and children.” But, that one minute of exposure to second-hand marijuana smoke was in rats, so it’s not clear how applicable this is to us beyond, perhaps, not smoking around your pets.

I have a slew of other videos on cannabis if you’re interested. Check out the related videos below. 

I first released these videos in a webinar, and you can find them all in a digital download here.