The following are key points to remember about this American Heart Association Scientific Statement on medical marijuana, recreational cannabis, and cardiovascular (CV) health:

1. The use of cannabis products, both recreationally and for medicinal use, has increased dramatically in the past two decades. During this time, the US policy and attitudes regarding cannabis use have changed significantly. Currently, in the United States, cannabis is considered either medical or recreational. The projected sales of legal cannabis are estimated at 23 billion dollars in the United States by 2025.
2. Cannabis products can contain pure tetrahydrocannabinol (THC) or cannabidiol (CBD) or a combination. Dosing can vary by product and route of administration. Approximately 30-60 minutes elapses before effects are experienced with oral administration. Peak effects are experienced approximately 3-4 hours after injection. Ingesting a high-fat meal can increase the absorption of oral cannabinoids and thus exacerbate the effects. Compared to cannabis products used before the mid-1990s, newer products have a significantly higher average THC content.
3. Potential benefits for many conditions suggest that use of cannabis may be of benefit for some. Cannabis effects have been associated with improvements in pain, cachexia, nausea and vomiting, and spasticity. These effects have led to the use of cannabis in various conditions, including fibromyalgia, chemo-induced nausea, multiple sclerosis, glaucoma, depression, and epilepsy.
4. However, the CV effects of cannabis are significant and may increase the risk of CV events among some adults. The effects of cannabis on the CV system are numerous. THC can stimulate the sympathetic system while inhibiting the parasympathetic system, leading to increased heart rate, blood pressure, and myocardial oxygen demand. Associations with endothelial dysfunction and oxidized stress have also been observed. CBD may reduce heart rate and blood pressure. Additionally, improved vasodilation and reduced inflammation have been observed. Long-term human studies are needed to determine CV effects.
5. Smoking and inhaling cannabis, regardless of THC content, has been shown to increase the concentrations of blood carboxyhemoglobin. Carbon monoxide intoxication is associated with endothelial dysfunction, oxidation of lipoproteins, and impaired oxygen binding.
6. Pregnant women are recommended to avoid cannabis use. Prenatal cannabis use is associated with increased risk of low birth weight. THC can enter the fetal brain through the maternal blood flow and has also been found in breast milk.
7. As with tobacco and nicotine products, smoked or vaporized cannabis is generally not recommended, especially in patients with respiratory diseases such as asthma or chronic obstructive pulmonary disease, and should be avoided in patients with severe liver disease because of the potential risk of fibrosis or steatorrhea. Driving a car or operating heavy machinery should be avoided because blood THC concentrations of 2-5 ng/ml are associated with substantial driving impairment.
8. Cannabis containing primarily THC (with little if any CBD), especially higher levels of THC, should not be used in patients with a personal history of psychiatric disorders (e.g., psychosis, schizophrenia, anxiety, and mood disorders); a history of substance abuse, including alcohol or concomitant psychoactive drugs; or a family history of schizophrenia because of the risk of exacerbation.
9. Because of variations in state laws, patients using cannabis should understand that although >30 states may have legalized cannabis for medicinal purposes, fewer than half protect patients from being fired or rejected for a job as a result of a positive cannabis test. Finally, interstate transportation of cannabis is a federal crime, even if the patient has an approved medical indication.
10. The negative health implications of cannabis should be formally and consistently emphasized in policy, including a doubling down on the American Heart Association’s commitment to limiting the smoking and vaping of any products and banning cannabis use for youth. All clinicians need greater exposure to and education on the various cannabis products and their health implications during their initial training and continuing education. The public needs high-quality information about cannabis. Research funding must be increased proportionally to match the expansion of cannabis use, not only to clarify the potential therapeutic properties, but also to better understand the CV and public health implications.

Clinical Topics: Heart Failure and Cardiomyopathies, Prevention, Smoking, Stress

Keywords: Blood Pressure, Cannabidiol, Cannabinoids, Cannabis, Carboxyhemoglobin, Dronabinol, Marijuana Smoking, Medical Marijuana, Nicotine, Oxidative Stress, Pregnancy, Primary Prevention, Psychotropic Drugs, Public Health, Public Health Practice, Smoking, Tobacco, Vasodilation

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