Medical studies have suggested that smoking cannabis regularly can lead to structural changes within a user’s heart.
Queen Mary University of London studied
the connection between smoking cannabis and heart function, with MRI images
being used from 3,000 participants including 152 current or former cannabis
It found that regular cannabis use can
enlarge the left ventricle (the main pumping chamber of the organ) and show
early signs of impaired heart function, which is of significant concern considering
the United States and Canada’s recent wave of cannabis legalisation.
ventricle is one of four chambers of the heart.
It is also the thickest of the heart’s chambers and is most vital as it is
responsible for pumping oxygenated blood to tissues all around the body, whereas
the right ventricle only pumps blood to the lungs. Negative effects impacting
the left ventricle can be detrimental to the heart and can lead to heart
problems and, in extreme cases, heart failure.
The average age of the participants in
the study was 62 while 55% of respondents were female. It also found that
regular cannabis smokers are more likely to be younger males who smoke tobacco
regularly and live in social deprivation.
Out of 3,407 participants, 3,255 had
rarely or never used cannabis, 105 had previously used it regularly but it had
been more than five years before they were interviewed and 47 were still using
The study found that the group still using cannabis regularly were more likely to have larger left ventricles and show early signs of impaired heart function, however there was no difference between all three groups in the mass of the left ventricle and the amount of blood ejected with each heartbeat.
Luckily, the study found that those
who had previously used cannabis regularly but had since quit had similar heart
size and function to the group of participants who had rarely or never used
“Our findings are not
conclusive but the research took place against a backdrop of decriminalisation
and legalisation of recreational cannabis use in many countries,” said lead
investigator Mohammed Khanji, MBBCh, PhD, senior clinical lecturer at Queen
Mary University of London.
“We urgently need systematic research
to identify the long-term implications of regular consumption of cannabis on
the heart and blood vessels.”
The new study comes after talk of the
UK potentially legalising cannabis over the next decade, with the Conservative
government seeming to be keen to latch onto the success of the emerging
industry across the Atlantic.
However, findings could put the UK’s
potential drive towards legalisation in jeopardy, which is in line with the
World Health Organisation’s comments about the possible
negative impact of cannabis when used in a non-medical instance.
“The World Health Organisation
has warned about the potential harmful health effects of non-medical cannabis
use and called for more research specifically around the cardiac impact,” added
“We believe this is the first
study to systematically report changes in heart structure and function
associated with recreational cannabis using cardiac MRI, which is a very
sensitive imaging tool and the current reference standard for assessing cardiac
It’s worth noting that the study
examined a variety of potential causes for heart issues including age,
diabetes, blood pressure, smoking and alcohol consumption.
The study could also be deemed
inconclusive as the sample size of regular cannabis smokers was actually very
slight compared to the total number of subjects examined. The sample also
included only 4% of people who are not Caucasian, adding to the limitations of
Many of the studies relating to heart
function and cannabis also have limitations in that cannabis use is rarely an
isolated instance, as it is often used alongside tobacco and alcohol or both.
Previous studies reiterate findings
While this was one of the first
studies examining heart function via an MRI scan, a study
from the American heart journal in 2013 found habitual cannabis use before a
heart attack was associated with a higher rate of death over the following 18
years. Although the difference wasn’t found to be statistically significant,
the summary suggests it to be beneficial for doctors to caution patients who
suffer from coronary heart disease and patients who have a high risk of
cardiovascular disease to abstain from smoking cannabis.
As previously reported
by the Leaf Desk, there has also found to be a worrying link between cannabis
use and mental illnesses. It’s known that depression can eventually become a
risk factor for heart disease, so cannabis use could also be attributed to
heart disease, although the link between cannabis and depression needs to be
Despite the fact that many claim that
cannabis in edible form is safer than when smoked traditionally, behavioural
scientist Dr Reid claims
that even edibles still have “some [effects] in terms of heart rate and blood
Edibles still most likely remain the
optimal choice for consumption, as it avoids the toxins commonly associated
with smoking cannabis being released as well as having a preferable reaction on
the oxygen carrying capacity of the blood, as smoking reduces the oxygen
transport through the body.
Dr Reid also suggested that the
correlation between cannabis use and heart disease is still “largely
theoretical”, however the existing evidence of cannabis potentially leading to
issues such as a quicker onset of excessive induced angina during a stress test
among people with heart disease, along with being a negative influence on those
who suffer from irregular heartbeat or arrhythmia demonstrates that those with
heart issues should converse with their doctor and take caution before using
Cannabis as medicine
It’s easy to discredit cannabis due to
its status as an illegal drug across the world for more than a century, but it
does in fact have numerous medicinal properties, with many patients solely
relying on it to treat a variety of illnesses.
And while cannabis may have a few side
effects, it has no more than traditional medication that can cause a series of
While unconfirmed, there has been speculation claiming that negative reports about cannabis are potentially being funded by big pharmaceutical companies who have a vested interest in keeping cannabis away from the shelves as it would subsequently reduce sales in the multi-billion dollar industry.