Editor's Note: This article was updated on December 20, 2019.
It’s no secret that cannabis isn’t a cure-all. While regular consumption for recreational purposes at the ever-increasing potencies available on the legal market today still appears to have a fairly low level of health risk for the average person, potential cardiovascular impact remains an important consideration for those managing heart disease.
Due to the legal status of cannabis in the United States, studies on cannabis-related cardiovascular events have been primarily observational and self-reported, often pulling from small population samples without differentiation of consumption method. Aside from an incident with a 90mg THC lollipop, almost all studied risks of cannabis on cardiovascular function are based on users of inhaled combustible cannabis – and there’s plenty of data to suggest smoking of any kind may be of particular concern for those with pre-existing cardiovascular disease (CVD). Obviously, more complete clinical data is still needed, but there are a few red flags to consider already in regard to cannabis and heart health.
According to an article published by Harvard Medical School, patients with established heart disease who were also under stress have reported an increased likelihood of chest pain after smoking cannabis. THC, the primary psychoactive substance in adult-use market cannabis, has been shown to increase resting heart rate, dilate blood vessels, and make the heart pump harder – particularly within the first hour after smoking – raising concerns about an increased risk of heart attack immediately after consumption. These effects may be compounded by amplified stress levels within an individual.
Of course, as access continues to outpace transparent consumer education on responsible use, over-consumption of THC and the anxiety-producing effects that intolerance to high potencies can bring may be exasperating the experience of increased stress as well. So, while THC or other cannabinoids may correlate with cardiovascular changes, many of these symptoms may be more directly associated with raised anxiety levels after consuming or even other unknown factors.
According to numerous reports of increased emergency room visits from panicked consumers following legalization - absent of an immediate and major cardiac event - cardiovascular stress from induced anxiety generally subsides quickly and may be mitigated through cannabis avoidance or carefully measured dosing. Someone with a pre-existing heart condition who finds needed pain relief from cannabis may still be able to consume without significant risk but should be in communication with a cannabis-educated clinician or trained consultant who can provide observation and guidance. However, acute symptoms in consumers with pre-existing cardiac concerns may not be the only cardiological consideration with cannabis.
Regular Cannabis Use Linked to Structural Changes in the Heart
In a report released this week in the Journal of the American College of Cardiology (JACC) on Cardiovascular Imaging, researchers at Queen Mary University of London have found a possible link between regular cannabis use and its impact on structural and functional changes to the heart.
Funded by the British Heart Foundation, researchers analyzed MRI cardiac scans from a UK Biobank population study of 3,407 individuals without a history of CVD and identified an association between regular cannabis use, defined as daily or weekly use, and an enlarged left ventricle – the heart’s primary pumping chamber. Of the total population sample studied, 105 patients reported regular cannabis use in the past and only 47 who continued to consume cannabis regularly.
Despite the acknowledged imitations of the study, including a small sample size of self-reported use and a heavy Caucasian skew (96%), the study authors noted larger left ventricles and early signs of impaired heart function in the continued-use group. Past users who had not consumed cannabis in the five years prior to the interviews had similar heart size and function to those who had rarely or never imbibed, suggesting these concerns may be short-term side effects. No significant differences in overall left ventricular mass or the amount of blood ejected with each heartbeat was found in the study and no changes in the size and function of the other three heart chambers were identified.
Lead author Dr. Mohammed Khanji, Senior Clinical Lecturer at Queen Mary, provided commentary for the news release on this first-of-its-kind study: "Our findings are not conclusive but the research took place against a backdrop of decriminalization and legalization of recreational cannabis use in many countries. We urgently need systematic research to identify the long-term implications of regular consumption of cannabis on the heart and blood vessels. This would allow health professionals and policymakers to improve advice to patients and the wider public."