Medical Cannabis for Chronic Pain Shows Link to Small Risk of Heart Rhythm Disorders

Danish analysis looks at the relationship between the therapy and cardiovascular adverse effects, particularly arrhythmias.

Cannabis prescribed for chronic pain is associated with an increased risk of heart rhythm disorders, according to the results of a study presented at the European Society of Cardiology Congress 2022.

“Chronic pain is a rising problem. According to Danish health authorities, 29% of Danish adults over 16 years of age reported chronic pain in 2017, up from 19% in 2000,” Nina Nouhravesh, MD, of Gentofte University Hospital in Denmark, said in a statement.

“Medical cannabis was approved in January 2018 on a trial basis in Denmark, meaning that physicians can prescribe it for chronic pain if all other measures, including opioids, have proven insufficient,”

“Safety data are sparse, hence this study investigated the cardiovascular side effects of medical cannabis and arrhythmias in particular, since heart rhythm disorders have previously been found in users of recreational cannabis,” she said.

In Denmark, medical cannabis can be prescribed in various formulations, including dronabinol, which is high in tetrahydrocannabinol (THC), cannabinoid, which has more THC than cannabidiol (CBD), and CBD.

The investigators of the study included about 1.6 million individuals in Denmark who were diagnosed with chronic pain between 2018 and 2021. Of those individuals, 4931 individuals claimed at least 1 prescription of cannabis, with 46% prescribed cannabinoids, 29% being prescribed dronabinol, and 25% prescribed CBD.

All individuals were matched by age, sex, and pain diagnosis to 5 individuals with chronic pain who functioned as controls.

Investigators followed those taking cannabis products and their controls for 180 days and compared the individuals’ risks of new cardiovascular conditions.

“Our study found that medical cannabis users had a 74% higher risk of heart rhythm disorders compared with non-users. However, the absolute risk difference was modest,” Nouhravesh said.

“It should be noted that a higher proportion of those in the cannabis group were taking other pain medications, namely non-steroidal anti-inflammatory drugs, opioids and anti-epileptics, and we cannot rule out that this might explain the greater likelihood of arrhythmias.”

The median age of the individuals was aged 60 years, and 63% were women. Approximately 17.1% of the individuals using cannabis products had arthritis, 14.9% had back pain, 17.8% had cancer, 3% had complicated fractures, 4.4% had headaches, and 9.8% had neurological diseases. Approximately 33.1% of individuals had other diagnoses, with the majority having unspecified chronic pain.

The absolute risk of new-onset arrhythmia was 0.86% in individuals using cannabis products compared with 0.49% in the control arm, with a relative risk of 1.74. Additionally, the risks of new-onset acute coronary syndrome and heart failure did not differ between the 2groups.

Investigators reported that the results were similar across chronic pain conditions and type of medical cannabis.

“This study indicates that there may be a previously unreported risk of arrhythmias following medical cannabis use. Even though the absolute risk difference is small, both patients and physicians should have as much information as possible when weighing up the pros and cons of any treatment,” Nouhravesh said.


Cannabis prescribed for pain linked with small risk of heart problems. News release. EurekAlert. August 22, 2022. Accessed August 22, 2022.