Cannabis treatment for chronic pain is associated with an increased risk of heart rhythm disorders

According to research presented at the ESC Congress 2022, cannabis prescribed for chronic pain is linked to an increased risk of heart rhythm disorders.


Dr. Nina Nouhravesh of the Gentofte University Hospital in Denmark, who authored the study, stated, “Chronic pain is a growing problem. In 2017, 29% of Danish adults over the age of 16 experienced chronic pain, up from 19% in 2000, as reported by the Danish health authorities.

In Denmark, medical cannabis was approved on a trial basis in January 2018, allowing physicians to prescribe it for chronic pain if all other treatments, including opioids, have failed. This study investigated the cardiovascular side effects of medical cannabis, in particular arrhythmias, since heart rhythm disorders have previously been identified in recreational cannabis users.


Depending on the levels of tetrahydrocannabinol (THC) and cannabidiol (CBD), various cannabis formulations are available for medical use. Denmark allows prescriptions for dronabinol (high THC), cannabinoid (more THC than CBD), and cannabidiol (high CBD). The medication can be inhaled, consumed, or sprayed in the mouth.


Between 2018 and 2021, the researchers identified a total of 1,6 million chronic pain patients in Denmark. 4,931 patients (0.31%) reported at least one cannabis prescription (dronabinol 29%, cannabinoids 46%, and cannabidiol 25%).

Each participant was matched by age, gender, and pain diagnosis with five non-users suffering from chronic pain who served as controls. Researchers followed users and controls for 180 days and compared their risk of developing new cardiovascular conditions.


Participants had a median age of 60, and 63% were female. The study reveals for the first time the chronic pain conditions of Danish medical cannabis patients. About 17.8% had cancer, 17.1% had arthritis, 14.9% had back pain, 9.8% had neurological diseases, 4.4% had headaches, 3.0% had complex fractures, and 33.1% had other diagnoses (mostly unspecified chronic pain).


In medical cannabis users, the absolute risk of new-onset arrhythmia was 0.86 percent, compared to 0.49 percent in non-users, for a relative risk of 1.74. The risk of new-onset acute coronary syndrome and heart failure was identical in both groups. The outcomes were comparable across all chronic pain conditions and medical cannabis types.


Compared to non-users, medical cannabis users had a 74% higher risk of heart rhythm disorders, although the absolute risk difference was small. This cannot be ruled out as a possible explanation for the increased risk of arrhythmias.


“Since medical cannabis is a relatively new drug for a large market of patients with chronic pain, it is essential to investigate and report adverse effects,” she concluded.

This study indicates that medical cannabis use may be associated with an unreported risk of arrhythmias. Even though the absolute risk difference is small, patients and doctors should have as much information as possible when weighing the benefits and drawbacks of any treatment.


Journal Reference

Richards JR, Blohm E, Toles KA, et al. The association of cannabis use and cardiac dysrhythmias: a systematic review. Clin Toxicol (Phila). 2020;58:861–869.

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