According to a study published in the European Heart Journal today (Thursday), people who take medical cannabis for chronic pain have a slightly increased risk of heart arrhythmias. Arrhythmia refers to when the heart beats too slowly, too quickly, or irregularly. This includes conditions such as atrial fibrillation.
While recreational cannabis use is associated with cardiovascular diseases, there are very few studies on the side effects of medical cannabis.
Researchers consider the new study important since more and more countries are allowing the use of medical cannabis for the treatment of chronic pain.
The study was led by Dr. Anders Holt from Herlev and Gentofte University Hospital in Copenhagen, Denmark. It included data from 5,391 Danish patients who were prescribed cannabis for chronic pain, including people with muscle, joint, or bone pain, people with cancer, and people with nerve pain. The researchers compared this group with 26,941 patients who also suffered from chronic pain but did not receive cannabis treatment.
The data showed that patients receiving medical cannabis had a 0.8% risk of being diagnosed with heart arrhythmia within 180 days of taking cannabis, which required monitoring and possibly treatment. This risk was more than double the risk for patients with chronic pain who did not consume cannabis. The risk difference between the two groups decreased when the researchers looked at the first year of treatment.
The study showed no connection between the intake of medical cannabis and the risk of an acute coronary syndrome, including a heart attack and unstable angina pectoris, stroke, or heart failure.
Medical cannabis is now allowed for the treatment of chronic pain in 38 US states, as well as several countries in Europe, such as Spain, Portugal, the Netherlands, and the United Kingdom, and elsewhere in the world. This means that more and more doctors are prescribing cannabis, despite the lack of evidence for its side effects.
I don’t think this research should deter patients with chronic pain from using medical cannabis if other treatments have been inadequate. However, these results suggest that improved monitoring may be advisable, especially for patients already at increased risk of cardiovascular diseases.“
Dr. Anders Holt from Herlev and Gentofte University Hospital in Copenhagen, Denmark
Researchers say that this is the first nationwide study of its kind to investigate the cardiovascular effects of medical cannabis in chronic pain. However, they point out that this is an observational study. Dr. Holt explained, „Despite our efforts to make a balanced comparison, it can never be assumed that patients prescribed medical cannabis do not differ from patients who were not prescribed medical cannabis, and this could influence the results.“
He added, „We need a lot more research in this area. Before coming to a conclusion, the results of this study should be replicated in other countries and settings. It would also be interesting to understand if there are any relationships between long-term cannabis consumption and heart conditions such as heart failure, stroke, or acute coronary syndrome. This would be an important area that needs to be clarified, as chronic pain can persist for many years.“
In an accompanying editorial, Prof. Robert L. Page from the University of Colorado, USA said, „A rigorous pharmacovigilance of cannabis, as well as its safety and efficacy, has been restricted by decades of worldwide illegality and the ongoing classification of cannabis as a Schedule 1 controlled substance in the US. Nevertheless, with the increasing decriminalization and legalization of cannabis worldwide, the association between cannabis exposure and cardiovascular events has emerged as an important safety signal.“
„Therapeutically, these results suggest that medical cannabis may not represent a uniform treatment option for certain conditions and should be contextualized based on the patient’s comorbidities and potential susceptibility to side effects.“
„Cannabis is typically labeled as recreational and ‚medical.‘ The latter terminology is under scrutiny as it encompasses cannabis products derived from phytochemicals, as well as prescription cannabinoids approved in the EU. Furthermore, the term ‚medical‘ implies that the product may have some clinical monitoring, safety, and efficacy data, which is far from the case for cannabis. In this sense, I would argue that ‚cannabis for therapeutic purposes‘ would be a more appropriate terminology than ‚medical‘.“
European Society of Cardiology
Holt, A., et al. (2024) Cannabis for chronic pain: cardiovascular safety in a nationwide Danish study. European Heart Journal. doi.org/10.1093/eurheartj/ehad834.