 Does the so-called dark side of cannabis include stroke? Here said to be associated with non-synthetic marijuana, by which I assume they mean marijuana. There have been case reports of artery damage due to the vasoconstrictor effect of cannabis, something that's been well documented. One study found cannabis users had 100 times greater odds of suffering from something called multifocal intracranial stenosis where the arteries inside your brain clamped down at multiple points, but that's a rare condition. What about strokes? The lack of high-level evidence regarding the adverse effects of marijuana usage on brain artery health has led to this notion that recreational marijuana may not be a problem, so they decided to put it to the test. You want high-level evidence? They said, well, how about a study of literally millions of pot smokers? OK then. And they found that recreational marijuana use did seem to be associated with an increased risk of being hospitalized with an acute ischemic stroke, but this may just be among those who smoke regularly, at least once a week. The reason we think it's cause and effect is that the majority of recorded strokes were during or shortly after marijuana exposure. There are even cases in which strokes recurred after marijuana re-exposure. So put all that together, and it makes a convincing case, though you really have to randomize people to smoke pot or placebo pot, to be sure. 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, the heart attack seemed to happen while they were using or right afterwards. However, this is complicated by the fact that cannabis 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 and make the connection without asking about other substance use. Within an hour of snorting cocaine, for example, the risk of having a heart attack goes up more than 20-fold. That's about five times more than after smoking pot. The hour after you smoke marijuana, your heart attack risk does appear to nearly quintuple, but only for that hour, then your risk drops down to normal. Okay, but what does that mean? Even though heart diseases are number one killer, the risk of having a heart attack every hour is only like one in a million in any particular hour. So even if you then light up a joint that may quintuple your risk, but that would only bump it to like one in 150,000 risk in that hour, but it's just for that one hour. So even if you smoked every day, your annual risk might just go up a few percent. But why the increased risk at all? Well, we've known since the 70s that within an hour of smoking a joint, pulse rate, goes up about 35%. Smoking a single joint increases blood pressure, too, as well as carbon monoxide levels in the blood of angina patients and cuts their ability to exercise nearly in half. Now, was that just because of breathing smoke? Any kind of smoke? No. Smoking a placebo joint, a joint with marijuana from which the THC has been removed, only cuts down exercise capacity like 9% compared to cutting the time they could exercise before the chest pain started by 48% with a cannabis. So it does seem to be a specific drug effect. Now, whether that's as bad as tobacco, we'd never know until a year later. Smoking a marijuana cigarette decreased the exercise time until angina more than smoking a tobacco cigarette, which only cut exercise capacity 23% compared to 50% after the joint. This may be because marijuana puts more demand on the heart, so no surprise then it was worse than tobacco. It may also be the carbon monoxide. Smoking marijuana leads to nearly five times more carbon monoxide in your bloodstream than smoking tobacco. This is because pot smokers inhale deeper and then hold the smoke in, allowing more carbon monoxide into your system. So between that and the cardio acceleration, the increased heart rate and pressure, that could account for the accelerated chest pain in heart disease patients. Does it have any chronic effects on our arteries? Cannabis users do seem to have relatively stiffer arteries for their age, suggesting an acceleration of the aging process, and we are only as old as our arteries. Even secondhand marijuana smoke may be harmful, according to this recent study in the Journal of the American Heart Association entitled, One Minute of Marijuana Second Hand Smoke Impairs Vascular Endothelial Function, meaning Artery Function. And so there was a call to protect vulnerable populations, including the elderly and disabled, and residents of multi-unit housing, pregnant women and children, even just one minute of exposure to marijuana secondhand smoke in rats. So it's not clear how applicable this is outside of perhaps not smoking around your pets.