While research into cannabis and its impact on all aspects of our health has undeniably skyrocketed in recent years, the internet is still jam-packed with contradictory reports of the true effects of the drug. As legalisation efforts continue to succeed in different parts of the world, it is important to be aware of both the negative and positive implications of cannabis use. So, with that in mind, we’re taking a closer look at cannabis and heart health, and asking: What’s the truth?
What do we mean by ‘heart health’?
Cardiovascular disease (CVD) is a term used to refer to conditions that affect the heart or circulation. High blood pressure, stroke, and vascular dementia, as well as conditions that narrow or block blood vessels (coronary heart disease), and conditions that affect the heart’s muscles, valves or rhythm, are all included under this umbrella term.
In recent years, the number of people living with cardiovascular diseases has seen a significant rise. It is now estimated that around 620 million people are now living with heart and circulatory diseases across the world – that’s 1 in 13 people! This figure is up from 350 million in 2000 and more than 430 million in 2010. As a result, cardiovascular diseases and stroke are the leading cause of death, globally.
This increase is likely due to a combination of factors, including population growth and ageing, rising healthcare inequalities, and an increasingly unhealthy population. But could cannabis use also be playing a role?
Cannabis and heart health
Cannabis is among the most widely used drugs in the world. Despite the high prevalence and long history of use, prohibition has meant that our understanding of the plant and its derivatives – and their health implications – remains substantially underdeveloped. This issue is highlighted by the lack of conclusive evidence of the effects of cannabis on the heart and its impact on cardiovascular disease.
But the fact is, cannabis is an extremely complex plant that not only contains hundreds (if not thousands) of active compounds but can also be consumed in a huge number of ways. For example, some consumers may opt for pure CBD products while others prefer high-THC; one user may use oils sublingually while another is loyal to smoking.
These variables, in addition to study design, may well make it difficult to understand the true effects of cannabis on heart health. But what does the evidence so far tell us?
Cannabis for high blood pressure
In a 2017 study, researchers aimed to measure the effect cannabidiol (CBD) had on blood pressure (hypertension) in healthy volunteers. To this end, nine male participants were given a single 600 mg dose of CBD or placebo in a randomized, placebo-controlled, double-blind, crossover study design. They concluded that “ resting blood pressure was lower after subjects had taken CBD and that CBD blunted the blood pressure response to stress”.
However, while the results may appear promising, the authors noted that further research was required to establish whether CBD has any role in the treatment of cardiovascular disorders. More recently, further research has been conducted; however, findings have been inconsistent.
In 2021, researchers from Ben-Gurion University conducted a prospective study of patients aged 60 years or older with hypertension and a new prescription for medical cannabis. They conducted 24-hour ambulatory blood pressure monitoring, ECG, blood tests, and anthropometric measurements prior to the initiation of cannabis therapy and 3 months afterwards. They found that cannabis treatment for 3 months was associated with a reduction in 24-hour systolic and diastolic blood pressure values.
These results were supported by the findings of a 2023 cohort study of 91,161 volunteers in the UK. It was found that both male and female cannabis users experienced lower overall blood pressure than non-users; however, the difference was deemed too small to recommend the adoption of cannabis-based medical products in a clinical setting.
Cannabis in heart attack and stroke
In early 2024, a new study made headlines in the US where researchers concluded that cannabis use was associated with increased cardiovascular outcomes. Data was taken from the Behavioural Risk Factor Surveillance Survey from 27 states and 2 territories and researchers assessed associations between cannabis use and self-reported cardiovascular outcomes (coronary heart disease, myocardial infarction, stroke).
According to the findings, daily cannabis users had a 25% higher likelihood of heart attacks and a 42% higher risk of strokes, while people who used cannabis just once a week were also at a slightly increased risk. Of the 434,104 respondents, 4% were daily cannabis users and 7.1% were nondaily users.
While these results are worrying, it is important to note that three-quarters of cannabis users reported smoking cannabis as their most common method of consumption and the study did not look specifically at the difference in risks between consumption methods. Smoking tobacco is largely associated with an increased risk of cardiovascular disease with the same possibly true for cannabis. It may therefore be difficult to separate the effects of smoking from the effects of active compounds within the cannabis plants, including cannabinoids.
Other implications on heart health
In 2019, a study by Queen Mary University of London concluded that regular cannabis use may be associated with structural changes to the heart. Researchers analysed MRI scans from 3,407 people (with an average age of 62) in the UK Biobank study who did not have cardiovascular disease.
They found that the people who regularly used cannabis (47 participants) were more likely to possess an enlarged left ventricle – the heart’s main pumping chamber, as well as early signs of impairment to heart function, compared with those who rarely or never used the drug (3,255 participants).
However, despite these differences, the study concluded that there appeared to be no difference between the three groups in the overall mass of the left ventricle or the amount of blood ejected with each heartbeat. Furthermore, as the lead author of the study, Dr Mohammed Khanji, noted:
“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.”
Once again – more research is needed
Associations between cannabis use and heart health remain a relatively new area of research. For this reason, it is difficult to draw certain conclusions on the drug’s implications in this setting. However, it is important to note that current research on this topic has an overwhelming focus on smoking as the primary administration method – a habit which is known to have a number of negative effects on various aspects of our health.
Recommendations from the World Health Organisation, as well as national bodies, indicate that people with or at risk of cardiovascular disease should cease smoking tobacco. Given the preliminary evidence, this advice may well be extended to smoking cannabis. Still, more research is required to better understand the effects of cannabinoids – including as a potential therapeutic – for heart health.
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