 So far, I've introduced you to cannabis and cannabinoids, and in my last video I discussed the impact of smoking cannabis on your lungs. In this video, I'll cover recent research on how cannabis use affects your heart and blood vessels, and we'll talk about some of the ways that cannabis has, in fact, killed people through overdose. A quick review of what we've learned about your endocannabinoid system. There are two receptors, CB1 and CB2. And while CB1 is found primarily in your brain and is responsible for cannabis' psychotropic effects, the CB2 receptor is found in a large number of tissues in your body, including your lung, your heart, blood vessels, and most especially your immune system. A common comment on previous videos was that, while most reasonable people agree that smoking cannabis joints is going to be bad for your lungs, other forms of ingestion don't carry the same risks. I want to be clear that this video is about harms that are irrespective of the mode of ingestion. Smoke it, eat it, vape it, it doesn't matter. The impact is from flooding your endocannabinoid system with a super stimulator drug. I'm going to break down the effects into two categories, acute and chronic. Acute responses happen quickly. Generally what people refer to as an overdose is called an acute toxemia. There is an acute toxemia for excess cannabis consumption that we'll discuss. The other response type is chronic long-term use of the drug, which causes effects on a longer time scale, over months or years or decades. Cannabis consumption also has cumulative chronic effects from long-term use. First the acute responses. When you ingest cannabis, the drug enters the bloodstream and circulates through the usual routes, eventually ending up in the brain where it has the desired psychotropic response. When stimulated, the cannabinoid receptors throughout your cardiovascular system have a two-phase response. Initially, vasodilation or relaxing of the blood vessels, which leads to increased blood flow. In some cases this can cause sudden drops in blood pressure, which causes people to faint, a position called postural syncope. At the same time, heart rate is often increased and may remain elevated for two to three hours. As dosage increases, that is as people get more stoned, the effect of relaxing blood vessels reverses and becomes vasoconstriction. We now have a very dangerous scenario, hard contracted arteries, a heart muscle pumping faster and harder than normal, and a sudden shift from low blood pressure state to a high blood pressure state. What can happen in rare cases is that the small blood vessels can't handle the pressure, and like a thin walled pipe bursts, producing internal bleeding, including bleeding in the heart and brain, called a hemorrhagic stroke. Alternatively, the pressure and blood flow can dislodge material from the blood vessel and produce a blockage or reduction in flow called an ischemic stroke. What distinguishes cannabis-induced stroke from just a random stroke from other risk factors in people who happen to be pot smoking at the time? Two things in particular. Cannabis-induced strokes occur in very young people, teens and 20-somethings, where all other risk factors could be ruled out. The second distinguishing feature is that these strokes recur again after smoking pot. There are numerous case reports of young people presenting with ischemic stroke who are successfully treated and then re-admitted a few weeks later with the same condition after the use of marijuana. Other than the blood pressure-related stroke risk, there's also a risk of damage to the heart muscle called cardiomyopathy and dysregulation of heart rhythms called atrial fibrillation, and the most extreme sudden cardiac death and myocardial infarction, commonly known as a heart attack. All of these are usually happening in young people, which makes them exceptional. So how big is this problem? For the most part, we don't know. The majority of publications on this topic are on specific case reports and forensic post-mortem reports, and we know these events are seriously under-reported because the linkage is not well known, even by clinicians. One study in France found that out of about 2,000 emergency room visits related to cannabis from 2006 to 2010, about 2% were serious cardiovascular complications, a total of 35 events, including 22 heart problems, 10 problems in limb circulation, and 3 strokes in the brain. 9 out of 35 of these events led to the death of the patient. That's a death rate of 26%. And on average, these were people in their 30s, who would not normally be at risk for heart attacks or strokes. Another study interviewed 3,800 recent heart attack patients. Of the 120 of them that were marijuana smokers, 37 were smoking within the 24 hours leading up to the attack. Based on a case crossover analysis, the authors of the study conclude that the risk of myocardial infarction, heart attack, was elevated 4.8-fold in the one hour following cannabis smoking. The second hour had only a non-statistically significant increase of 1.7-fold, which further suggests that the drug may have triggered the attack. I want to be clear, these are likely very rare events, and we know little about what triggers them beyond an understanding of how phytocannabinoids interact with the cardiovascular system. The fact that they're so serious, and that so few people are even aware of these risks, make this topic worth studying more. I'm frustrated with the myth that no one has ever died from cannabis overdose, especially when offered by people I consider to be pro-science and pro-evidence. While it's hard to get a specific number of deaths resulting from rare cardiac complications of acute cannabis use, I find it highly unlikely that any drug that changes blood pressure and cardiac output has a zero death rate. Let's shift the focus from acute responses to chronic effects of long-term cannabis use on the cardiovascular system. There are only two effects I want to highlight, cannabis arteritis and alterations in normal heart function. Arteritis is inflammation in the walls of an artery. Cannabis arteritis is a poorly studied consequence of long-term cannabis use. If you recall, cannabinoid receptors are found on immune cells. Those immune cells are found along the lining of blood vessels, and chronic stimulation may cause them to produce an immune response with the effect of hardening the arteries or producing clots. When this occurs in the extremities, toes and fingers, the result is necrosis or tissue death followed by gangrene. And in many of the case studies, patients who are unable to stop using marijuana require amputation of the affected digit. The complication with studying cannabis arteritis is that so many people use both tobacco and cannabis, and tobacco is a known risk factor for arteritis. The only distinguishing factor is that, again, these case studies are mostly in young people who wouldn't normally be at risk from tobacco use alone. It's possible that tobacco plus cannabis is the real risk factor. More study is needed. Lastly, cannabis use can disrupt the normal function of the heart. It does this through interacting with the adrenergic system of your body, the one responsible for regulating your heartbeat. A number of cannabinoids found in marijuana interact with both the part of your brain responsible for heart function, but also directly with the adrenal response in your heart by altering the way the nerves there respond to the signals. Chronic use of cannabis is associated with heart rhythm defects, atrial fibrillation, tachycardia, palpitations and premature contractions. This is, again, very poorly studied and understood. The effect on most people is probably below detection. But in people with complications, like a congenital heart defect or congestive disease, cannabis can increase risk of death. I focused on negative consequences of recreational use, but I think it's worth recognizing that for every harmful interaction with the body, there's an opportunity to develop cannabinoid drugs that correct other types of defects. The impact of cannabinoids on stroke survival, for example, is an exciting area of research. As are applications in diseases of the central nervous system and immune disorders, I feel very strongly that therapeutic use and recreational use should be treated as two separate cases. By analogy, codeine is a very effective cough medication. But it's potentially habit-forming and a popular drug of abuse. I can talk about the medical use of drugs, including synthetic cannabinoids, without discounting the health consequences of recreational use. If you take only a single message away from this video, I hope it's this. Cannabis use in any form carries with it some potential for rare but life-threatening conditions. I'm not trying to scare anyone. Being informed is not the same as being afraid. Cannabis use of any kind will carry with it risks, typically in proportion to dose and duration of use. I feel about cannabis use the way I feel about tobacco use. I'm not interested in judging or shaming you, but I hope through education to make sure you make an informed decision on the best research. As always, consult your physician or health care provider if you have questions or concerns. Never take your health advice solely from the internet. The next video in this series is going to attempt to cover the impact of cannabis use on the brain. I'll talk about the scientific basis for reefer madness and the growing body of evidence linking early cannabis use and psychosis risk. I'll also talk about the long-term cognitive consequences, IQ, learning ability, and we'll touch on risks associated with driving while stoned. I look forward to your comments and thanks for watching.