Cannabis and the Cardiovascular System


     The Cardiovascular system (CV) involves the heart, arteries, veins, capillaries, and all the components of the circulatory system including neural control over heart rate and rhythm, blood flow, and blood pressure. The use of medical cannabis in patients with cardiovascular disease (CV) and cardiac conditions is a complicated and little researched subject.  There are studies that show some protective benefits of cannabis for the CV system and your heart, while other studies and research show risk and contraindications to its use. Most of these studies concern the THC portion of the cannabis plant (other cannabinoids also warrant attention), and most studies only involve specific ingestion (i.e. smoking). Due to the large numbers of components in cannabis and the variety in dosing and ingestion techniques, as well as to other factors such as cigarette smoking and concomitant drug use of alcohol and other substances, research results are cloudy and difficult to substantiate.

      It is particularly important that existing cannabis patients with heart disease should be aware of some of the possible detrimental effects. New users of cannabis should also be cognizant of possible issues that may arise with THC or cannabis smoking.  One purpose of this article is to determine the overall safety in using medical cannabis in patients who are diagnosed with cardiac or circulatory issues. These conditions would include coronary bypass patients, those with high blood pressure, and those that have had coronary arterial stents placed. Some other conditions that patients may have would include cardiac arrhythmias and tachycardia (elevated heart rate), atrial fibrillation, syncopal events (fainting), stroke, transient ischemic attacks (TIA’s), coronary artery disease (CAD), cerebral hemorrhage, and arteriosclerosis (plaque buildup inside the arteries). There are a host of other cardiac and circulatory issues not covered in this article, and the above conditions will be among those topics addressed in this article.

     A substantial number of medical cannabis patients in Maryland are older and have relevant cardiovascular issues affecting their health and are questioning the safety of using medical cannabis. The approved use of medical cannabis in our state results in more individuals using cannabis for other reasons (i.e. anxiety, insomnia, etc..) with possible negative side effects on CV health. It is important to recognize that the vast majority of patients can use cannabis safely and any detrimental effects on the heart are not a relevant issue. While it is generally not contra-indicated, and large numbers of CV patients use cannabis without adverse effects, those patients using high THC should be aware of any associated risks. Also, all new users of cannabis should be briefed on any adverse cardiovascular dangers that may be a factor in their use of medical cannabis.

     A fairly large percentage of cardiologists in the medical profession do not typically deal with cannabis but should recognize it is a medicine that a lot of their patients may be using. Many logically equate it with tobacco use and smoking and are opposed to its use due to the widely known detrimental effects of cigarette smoking on health. However, cannabis has no nicotine in the plant and does not always involve smoking. Other cardiologists may recognize some of the benefits of cannabinoids on heart health and be in favor of some uses of the plant (*i.e. CBD). Those knowledgeable in cannabis research should be aware of some of the beneficial effects that can result from using cannabis. For example, those with chronic or severe anxiety may reduce overall load and stress on the heart if cannabis helps to combat their original anxiety. They may also feel less stressed as they eliminate unnecessary pharmaceutical drugs commonly used to treat anxiety and switch over to using cannabis.

     Patients with heart disease should certainly seek regular cardiac care and advise their cardiologist of their use of cannabis, and how they consume it. For some heart issues, it can be relatively benign or perhaps beneficial to use cannabis or extracts from the plant, and for others, for example in those with atrial-fibrillation or ventricular tachycardia, or a history of heart disease will need to use with caution. Some caution is also advised for new and naïve first-time users of medical cannabis, especially THC, as occasional CV events are possible - as may happen with vasodilation causing dizziness and/or fainting.

     Since there are several hundred compounds in the cannabis plant, when speaking about cannabis and heart disease it is important to understand which exact compounds are being referenced. Usually, most studies involve THC and CBD alone or in various ratios combined together.  Research studies also commonly involve mice and synthetic cannabinoids and occasionally humans, although this is changing as laws become less restrictive and more human trials are conducted. In addition, most studies do not include any of the other cannabinoids (CBC-CBDV-CBN-CBG, etc.) that are found in the cannabis plant. The terpenes, flavonoids, plant phenols, and sterols found in the cannabis plant are likewise not included in most of the research. Dosages, ingestion techniques, and methods of use also play a large role in the outcome and results of any studies conducted, as well as concomitant use of other drugs.


     Let’s examine some of the studies, both in lab animals (mice), test tubes (lab), actual primates (monkeys), and finally humans.
Some of this research is sparse, limited, and anecdotal. For example, the International Cannabinoid Research Society (I.C.R.S.) has conducted limited or very generalized research studies on this topic. Other research groups often focus on different diseases, and more studies are needed dealing with cardiovascular issues and cannabis. Currently, there are perhaps a dozen or so major studies ongoing or completed. These studies will both elucidate any risks associated with cannabis and heart disease, as well as possibly uncover some benefits as well. Specific cardiovascular situations that may benefit from cannabis may require different cannabinoids, similar to the discovery that different cancer cell types respond to different groups of cannabinoids. In addition to the cannabinoids, other compounds in the plant (i.e. flavonoids, terpenes, plant sterols, polyphenols, etc.…) may also play a role in cardiac and circulatory diseases, or alterations of cardiac health both good and bad. Some protective effects on the heart and CV system have been noted but they are generally outweighed by possible detrimental effects.


     Cannabis has well-known effects on the cardiovascular system. Typically, these effects are mediated thru the CB1 and CB2 receptors. Other receptors may also be involved (PPAR, TRPV1) but the THC component of cannabis is most often studied and it’s effects mediated through the CB1 and CB2 receptors. These receptors have been shown to play a beneficial role in modulating cardio-metabolic risk, and atherogenesis, and may also have a role in limiting cardiac muscle damage. These g- protein-coupled receptors are located on the cell membranes in many locations of the body including inside the heart, on all blood vessels and also some blood cells. In animals, one effect of cannabis (i.e. THC) on the cardiovascular system is to dilate blood vessels (a vasodilator) and reduce or lower blood pressure (hypotension). In humans, this effect is similar but not as pronounced. Initially, in naïve or new users blood pressure and pulse can be elevated for a period of hours, but this effect tends to be reduced with long-term chronic use. In fact, long term users who have had no adverse heart or circulatory effects may be more tolerant and protected from adverse effects. There is some research being performed to use cannabinoids as a blood pressure reducing agent.

    When smoking cannabis your circulatory system dilates, both through central nervous effects and also local effects directly on your blood vessel receptors, and your pulse rate goes up to compensate. Therefore, it is quite a common occurrence for pulse rate to be elevated significantly after cannabis use. This elevation can persist for up to three hours and is most significant especially in the first hour after use. Your pulse rate may go up by as much as 20% - 50% over your normal pulse. Once again, experienced users have a more minimal effect. Also, hypotension or low blood pressure can occur quickly and induce fainting or loss of consciousness in some initial users of THC who have done too high a dose. Postural, or orthostatic hypotension can also occur which causes dizziness or fainting upon standing up from a lying or sitting position. Experienced users have been shown to quickly develop tolerance to these effects and they become less pronounced.

     It is postulated that the endocannabinoid system (ECS) plays a key role in modulating many vascular functions and this system is necessary for proper homeostasis in cardiac regulation. Cannabis use is not associated with any serious cardiovascular issues for most young healthy users, although occasional myocardial infarction, stroke, and arrhythmias have been reported. These may be random events not directly related to cannabis, or caused by contaminants in the plant or concurrent use of other drugs (tobacco, alcohol, narcotics, amphetamines, MDMA, etc.). Nonetheless, there are enough studies to date that warrant close attention and further research. Some of the detrimental effects of THC on the CV system are widely reported and seen in overlapping studies from different areas of research. For this reason, these studies should be examined carefully, and the harmful effects brought to light to ensure the safe use of medical cannabis and your heart. We will focus on some of these negative issues and adverse effects users should be aware of, and this research comes from an aggregate of multiple studies conducted over the last ten years. Marijuana smoking by those with CV disease can pose a health risk resulting from the increased cardiac workload, increased catecholamine levels, production of carboxyhemoglobin, postural hypotension, increased risk of stroke, myocardial infarction, cardiac ischemia, and rhythm irregularities. While examining these issues, the relative incidence in patient populations is relatively low but users should be made aware of these adverse effects.


Some of these negative adverse effects are:


*Increase in heart rate 20%-50% in acute or new users, while in chronic user’s tolerance can develop to decrease heart rate.

*Increase risk of cardiac arrhythmia – ventricular tachycardia or atrial fibrillation (more common in young healthy males).

*Increased risk of myocardial infarction and ischemic stroke, particularly in younger healthy patients. This is controversial…

*Increase in cardiac angina events.

*Decrease in cerebral blood flow – increasing the risk of cerebral vascular accident (CVA) or transient ischemic attack (TIA).

*Orthostatic Hypotension resulting in dizziness or fainting, accompanied by rapid heart rate and drop in blood pressure – usually reversible and non-life-threatening.

*Cannabis induced Vasospasms – arterial coronary vasospasms can induce cardiomyopathy.

*Increased risk in of infarction - patients with coronary artery disease, stents, or bypass surgeries – although some evidence shows no increase in death rate.


The effect of cannabinoids on the CV system is broadly diverse and complex. In spite of the above POSSIBLE adverse effects, these studies generally only involve THC and smoking. In addition, there are also many variables not tested for - such as additional drug use. Patients who have a cardiologist almost by definition have some CV issue and they should inform their physician about their use of cannabis to promote better care and also advance knowledge in the field.

These warnings and adverse effects listed above are often rare and not totally clinically substantiated. However, there does seem to be general agreement across multiple studies over time.

 The risk verses reward of cannabis use needs to be weighed. It is probable that alternate ingestion techniques to smoking such as vaping, tinctures, edibles, etc.… can be safer than combustion and may not be as harmful to your cardiovascular health. Moderation in dosages and slow onset ingestion techniques can prove to be safer. It is also true that cannabis can help prevent excessive weight gain and combats the metabolic syndrome, thereby leading to better circulatory and cardiac outcomes. In terms of risk - dabbing, concentrate use, and high THC rapid ingestion may exacerbate the negative side effects. Other cannabinoids often located in the plant may also exert protective effects and lessen adverse effects, or play a cardio-protective role. CBD has been effective in this regard. Other plant components may prove to be of benefit in CV disease and not yet be identified or researched. The vast majority of patients with CV disease will have no harmful effects from using cannabis wisely, but should be cognizant of adverse effects and be aware of the risks.


Dr. Stanley R. Manstof

12201 Greenridge Drive

Boyds, Md. 20841

*MMCC Certified Provider

*American Academy of Cannabis Physicians

*Member Americans for Safe Access

*Technical Writer and Editor

*Member Society of Cannabis Clinicians

*International Cannabinoid Research Society

                          *I.A.S.P. Imperial College of London Cannabis Research

*Certified Patient Caregiver

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